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AIMS: The study investigated the association between clinical symptoms and late-onset sepsis (LOS) in preterm infants with the aim of identifying a non-invasive tool for the early detection of LOS. METHODS: This was a prospective study of 83 episodes of suspected LOS in 67 preterm infants. At the time LOS was suspected, we recorded a standardized set of clinical symptoms. A diagnosis of "clinical LOS" (Clin-LOS), "culture-proven LOS" (Prov-LOS) or "LOS not present" (No-LOS) was made on the basis of C-reactive protein (CrP) and blood culture results where Clin-LOS was defined as CrP>10mg/l, Prov-LOS was defined as CrP>10mg/l AND positive blood cultures, or it was established that there was no sepsis present (No-LOS). We examined univariable associations between clinical signs and LOS using odds ratio (OR) analysis and then adjusted the odds ratio (adOR) through binary regression analysis. RESULTS: Clin-LOS was diagnosed in 20/83 episodes, 19 cases were found to have Prov-LOS. Clinical signs which had a significant association with Clin-LOS were capillary refill time >2s (OR 2.9) and decreased responsiveness (OR 5.2), whereas there was a negative association between gastric residuals and LOS (OR 0.35). However, the most marked association was found for a greater central-peripheral temperature difference (cpTD) >2°C (OR 9). In Prov-LOS an increased heart rate (OR 3.1), prolonged capillary refill time (OR 3.3) and again an increased cpTD (OR 16) had a significant association with LOS, whereas gastric residuals were negatively associated (OR 0.29). Regression analysis showed that cpTD was the most striking clinical sign associated with both Clin- (adOR 6.3) and Prov-LOS (adOR 10.5). CONCLUSIONS: Prolonged capillary refill time and - more impressive - elevated cpTD were the most useful clinical symptoms for detection of LOS in preterm infants. We especially suggest using cpTD as a predictor of LOS. It is a cheap, non-invasive and readily available tool for daily routines.

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The rates of delivery by Cesarean section (CS) have been trending upwards in recent decades, perhaps leading to higher rates of dysfunction in respiratory adaptation in newborns. We present epidemiological data for pulmonary adaptation by mode of delivery for healthy late preterm and term infants born at a regional tertiary care center. The overall CS rate was 22% with the largest proportion of these in late preterms (39%). This drops to 30% in infants born after 37 weeks gestation and to 11% for those born after 40 weeks. Infants needing respiratory support decreased significantly as gestational age increased: 88% at 34 weeks, 67% at 35 weeks, 28% at 36 weeks, 17% at 37 weeks and 8% at 40 weeks. The risk of respiratory morbidity following CS as compared to vaginal delivery (VD) was substantially higher. 50% of infants born by CS needed respiratory support compared to only 12% following VD. 82% of all late preterm infants born by CS developed respiratory morbidity compared to 36% following VD. Comparable data for infants born after 37 and 40 weeks gestation were 33% compared to 9% and 26% compared to 6% respectively. Late preterm infants born after 36 weeks gestation showed the most marked difference by mode of birth with 66% needing respiratory support following CS as compared to only 9% following VD. Our data could be useful in counselling parents about risk associated with delivery by Cesarean section. A critical view should be taken of increasing CS rates worldwide because of a clear correlation in increased morbidity in infants, especially late preterm infants.

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OBJECTIVE: The study investigated the ability of near-infrared spectroscopy (NIRS) to detect subgroups of preterm infants who benefit most from red blood cell (RBC) transfusion in regard to cerebral/renal tissue oxygenation (i) and the number of general oxygen desaturation below 80% (SaO(2) <80%) (ii). STUDY DESIGN: Cerebral regional (crSO(2)) and peripheral regional (prSO(2)) NIRS parameters were recorded before, during, immediately after and 24 h after transfusion in 76 infants. Simultaneously, SaO(2) <80% were recorded by pulse oximetry. To answer the basic question of the study, all preterm infants were divided into two subgroups according to their pretransfusion crSO(2) values (<55% and ≥55%). This cutoff was determined by a k-means clustering analysis. RESULT: crSO(2) and prSO(2) increased significantly in the whole study population. A stronger increase (P<0.0005) of both was found in the subgroup with pretransfusion crSO(2) values <55%. Regarding the whole population, a significant decrease (P<0.05) of episodes with SaO(2) <80% was observed. The subgroup with crSO(2) baselines <55% had significant (P<0.05) more episodes with SaO(2) <80% before transfusion. During and after transfusion, the frequency of episodes with SaO(2) <80% decreased more in this group compared with the group with crSO(2) baselines ≥55%. CONCLUSION: NIRS measurement is a simple, non-invasive method to monitor regional tissue oxygenation and the efficacy of RBC transfusion. Infants with low initial NIRS values benefited most from blood transfusions regarding SaO(2) <80%, which may be important for their general outcome.

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BACKGROUND: The accurately timed extubation of ventilated ELBW preterm infants is still a problem. With different data systems the attempt has been made to more accurately predict the successful extubation of these infants. However, there do not yet exist any satisfying solutions. PATIENTS/METHODS: We retrospectively analysed 66 ELBW preterm infants who were endotracheal intubated and ventilated within 24 h postnatal. Basic data, clinical and ventilation data immediately before planned extubation and in several intervals during the following 24 h, as well as outcome variables at discharge were interpreted. RESULTS: 51 patients were successfully extubated (EE-group), 15 (22.7%) failed extubation (reintubation within 48 h after extubation, EV-group). Immediately before extubation in the EE-group there was found a significantly higher inspiratory oxygen concentration (FiO2) in comparison to the EV-group (0.25 vs. 0.3; p=0.01). After the extubation attempt the inspiratory oxygen concentration stayed lower in the EE-group, whereas in the EV-group it rose remarkably (2 h after ext.: 0.26 vs. 0.4; p<0.001). Neither of the basic data showed any significant difference. The outcome analysis indicated a longer intensive care in the EV-group and a trend towards increased BPD and ROP. CONCLUSION: The study shows that for ELBW preterm infants the inspiratory oxygen concentration is especially important to predict a successful extubation. According to our data, the inspiratory oxygen demand before and immediately after extubation establishes the essential difference between successfully extubated and reintubated infants.

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BACKGROUND: Rapid enteral feeding volume advancement in preterm infants can reduce the use of intravenous fluids. This practice may decrease the hazards of intravenous infusion solutions and potentially the morbidity rate. Several cohort trials demand the standardised nutritional regimen to reduce the complications and the time to reach full enteral feeds. AIM: to determine whether using a standardized nutritional regimen the rapid enteral feeding advancement in preterm infants is practicable without increasing the incidence of feeding complications. PATIENTS AND METHODS: A prospective, randomized, controlled trial was performed in 99 preterm infants, birth weight ≤1,750 g. Group ST (standardized nutritional regimen) received breast human milk according to a standardized nutritional regimen. Group IN (individual nutritional regimen) received breast human milk or semi-elemental nutrition (Pregomin(®) Milupa) depending on enteral problems of the infant. The feeding volume advancement in the IN-Group was decided individually. The main outcome measure was time to reach full enteral feedings. RESULTS: Infants in the ST-Group achieved full enteral feedings after 14.93±9.95 (median 12) d, infants in the IN-Group after 16.23±10.86 (median 14) d. The difference between the groups was significant only in small for gestational age (SGA) infants: ST-Group 10.20±4.78 (median 8.5) vs. IN-Group 16.73±8.57 (Median 15) days (p=0.045). The weight gain was similar in both groups. Infants in ST-Group achieved full enteral feedings having 116% of birth weight, infants in IN-Group 122% of birth weight. This difference was not significant (p=0.195). The incidence of NEC (necrotizing enterocolitis, 4%) and other complications were low in both groups. The diagnosis "feeding complications" was described in IN-Group in 14 vs. 7 infants in ST-Group. CONCLUSIONS: SGA-infants profit from the enteral feeding advancement by using a standardized nutritional regimen. These infants achieved full enteral feedings sooner then the SGA-infants, who did not feed by using a standardized nutritional regimen. A standardized nutritional regimen can be realized in clinical routine and is by strict clinical observation practicable without increasing the incidence of feeding complications.

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OBJECTIVES: The purpose of our study was to establish reference intervals for thyroid function tests in children and adolescents and to identify factors that may influence the limits of these intervals. METHODS: TSH, FT3, FT4, T3, T4, t-uptake, TPO-antibody (TPO-Ab) and TG-antibody (TG-Ab) levels were determined in blood of 1004 infants, children and adolescents by the Elecsys system (Roche). RESULTS: A distinct overall age-dependent decrease of analyte levels was found for all parameters investigated. Puberty was accompanied by an increase of TSH, FT3 and T3 levels. Results of T4 and t-uptake were significantly higher in girls compared to boys. The exclusion of children with increased TPO-Ab and TG-Ab had no significant effect on the limits of the reference interval. We found that besides age, BMI-SDS but also white blood cells count and gender played a role in the prediction of analyte variation. CONCLUSIONS: Covariates like BMI-SDS and white blood cell count should be taken into consideration when interpreting TSH and thyroid hormone measurements as well whereas gender and TPO-Ab or TG-Ab play a minor role.

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BACKGROUND: CPAP is widely used in preterm infants on NICUs but it poses a stressful stimulus to the patient, sometimes requiring the use of analgosedative drugs. AIM: The aim of this study is to evaluate the risks and benefits associated with the use of low-dose morphine in preterm infants with CPAP, especially apnea. METHODS: Sixty-four CPAP-treated preterm infants, who received a low single dose of morphine (recommended 0.01 mg/kg), were included in this prospective study. Observation-time was 4 h prior to injection, directly before injecting, until 15 min and 15-30 min, 30 min-1 h, 1-2 h, 2-3 h, 3-4 h, 4-5 h and 5-6 h after injection. For all observation periods incidence of apnea, heart rate, respiratory rate and a score for analgesia and for sedation were recorded. RESULTS: Sixty-four preterm infants (29.6+/-3.3 weeks gestational age (GA), birth weight 1401+/-735 g) received 0.025+/-0.012 mg/kg morphine i.v. on the day 10-13 of life. The decrease in heart and respiratory rate, scores for analgesia and sedation were significant. The overall incidence of apnea did not increase compared to the 4 h pre-morphine period. Six patients (9.3%) experienced considerable delayed apnea. This group was significantly younger in GA (p<0.001) and lighter in birth weight (p=0.002). CONCLUSION: Morphine in dosage less than half of recommended dosage has a high analgetic and sedative potential. The danger of delayed severe apnea has to be taken into consideration in the clinical situation, especially in patients<28 weeks.

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BACKGROUND: Infants of drug abusing mothers are at high risk to suffer from neonatal abstinence syndrome (NAS). Depending on the drug signs of neonatal withdrawal vary but mainly include central nervous system irritability. NAS causes long duration of hospital stay. Severe withdrawal signs are seen in infants exposed to methadone, infants exposed to other opioids like heroin or buprenorphine have been shown to be less symptomatic. Between the years 1997 and 2003 following the border opening there was a dramatic increase in drug exposed newborns seen in the area of Leipzig (East Germany). METHODS: In a retrospective study maternal and infant characteristics, severity of symptoms, duration of withdrawal and hospital stay, duration and kind of treatment as well as modalities for release from hospital were analyzed. RESULTS: From 1997 to 2003 49 drug exposed newborns were admitted to our neonatal care unit. There was an increase of the number of affected infants within these years ( ). Maternal drug abuse (n=48) included mainly methadone (n=33), in second line heroine and benzodiazepines, in a few cases also cocaine and cannabinoides. 3 mothers received substitution therapy with buprenorphine. Additional drug use to substitution therapy was seen in 15 mothers. Drugs of abuse were detected in infant urine specimen (36/48). 35 of exposed newborns showed signs of NAS (incidence of NAS 71%). For evaluation of withdrawal signs and conduction of therapy the Finnegan score was used. As first line pharmacological treatment phenobarbitone was administered (n=42), secondary morphine was used (n=14, treatment failure 33%). Mean duration of hospital stay was 21 days. Mean duration of pharmacological treatment was 14 days with longer duration for methadone exposed infants vs. non-methadone exposed infants (16 vs. 10 days). Hospital stay was longer for non-methadone exposed infants. Maternal intake of more than 20 mg methadone per day vs. up to 20 mg per day caused longer duration of hospital stay (28 vs. 20 days, p=0,015). CONCLUSION: Long duration of hospital stay and pharmacological treatment call for optimised principal guide lines for diagnosis, treatment and long term follow-up. The results also underline the need for further research for an effective pharmacological treatment.

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BACKGROUND: The aim of the study was the description and review of a diagnostic management for treatment of patent ductus arteriosus in preterm neonates. Indomethacin, widely used to effect nonoperative closure of patent ductus arteriosus, has been implicated in vasoactive side effects and requires an accurate diagnosis. PATIENTS AND METHODS: Firstly, the hemodynamic significance of the ductus arteriosus was assessed by clinical signs, such as tachycardia, disturbed microcirculation and a high difference of central and peripheral temperature. The patent ductus arteriosus was confirmed by echocardiography. The left ventricular systolic time intervals and the cerebral perfusion were obtained by pulsed doppler recordings. 48 preterm infants below 1500 g were investigated within the first 12 hours of life and during the first week. RESULTS: In 32 preterm neonates (67 %) a patent ductus arteriosus without hemodynamic significance and in 9 neonates a patent ductus arteriosus with hemodynamic changes was detected. In 9 neonates there were no signs of patent ductus arteriosus. Neonates with typical clinical signs of patent ductus arteriosus exhibited significantly diminished preejection time, prolonged ejection time and a decreased quotient of preejection and ejection time. We found pathologically changed parameters of anterior cerebral artery in neonates with clinical signs of patent ductus arteriosus. To judge the efficiency of the diagnostic management the groups of neonates were compared concerning the evidence of complications. Neonates with ductus arteriosus but without therapy did not reveal more pulmonary problems as well as intracerebral hemorrhages, renal or intestinal disturbances than the group of neonates with treated ductus arteriosus. CONCLUSIONS: Summarizing, we suggest that the described criteria are to be taken into account before treatment of ductus arteriosus in preterm neonates. In this way a wide clinical and echocardiographical investigation will be performed in risk neonates and a useless therapy can be avoided.

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Serum leptin levels reflect body fat mass (FM), and have been described to be related to serum uric acid levels in adult type 2 diabetic and healthy subjects. We therefore aimed to evaluate the interrelationship between leptin and markers of the metabolic syndrome by studying serum leptin concentration, body mass index (BMI), percent body fat (Fat%), total fat mass (FM), sum of skinfolds (SS), triglycerides (TG), total cholesterol (CHOL), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), glucose, insulin, calculated insulin resistance (HOMA), creatinine (CR), and uric acid (UA) concentration in 50 former small-for-gestational-age (SGA) children and 21 infants born adequate for gestational age (AGA) at the time of mid-puberty. Our data confirm previous results showing a positive association between leptin and body fatness, and female gender. Twelve children with impaired glucose tolerance (IGT) had higher UA levels than subjects with normal glucose tolerance (NGT) (5.1 +/- 1.1 v 4.2 +/- 1.2 mg/dL, P <.05), and showed the strongest relation between serum leptin and UA (r =.76, P <.001). Multiple regression analyses demonstrated that gender, estimates of total body adiposity (Fat% and SS), birth weight (BW), gestational age (GA), stimulated glucose and insulin, and serum UA are independently associated with serum leptin concentration in former SGA children with dysglycemia (R(2) =.89, P <.001). A long-term effect of intrauterine growth restriction on body fatness, metabolic syndrome, and serum leptin levels is suggested.

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UNLABELLED: The aim of this study was to evaluate the accuracy and safety of transcutaneous bilirubinometry in preterm infants using the new bilirubin analyser BiliCheck. The study included 145 preterm children (23-36 wk gestation). Capillary blood sampling for determination of serum bilirubin (BS) was combined with transcutaneous bilirubin measurement (BTc) every morning until the sixth postnatal day and related to several clinical data (phototherapy (PT), infection signs, breathing disturbances, skin bleeding, etc.). Overall bilirubin concentration ranged from 17 to 371 micromol/l, and from 21 to 325 micromol/l for BS and BTc, respectively. Mean values obtained by BTc were significantly higher than BS values. The correlation coefficient between BS and BTc was r= 0.64 for the whole group, and r = 0.73 in infants without PT. As demonstrated by multiple regression analysis, BS-BTc correlations were related only to gestational age (beta -0.32) and breathing disturbances (beta 0.29), indicating that the lower the gestational age and the more seriously ill the baby, the higher the incoherence between BS and BTc. CONCLUSION: BiliCheck provides a convenient, non-invasive possibility for bilirubin estimation in preterm infants. However, there are limitations: the method gives reliable results only in newborns older than 30 wk gestation, without PT and artificial ventilation.

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Valproic acid (VPA) has been considered as a possible treatment agent for malignant gliomas. In order to characterise the possibilities of VPA, we investigated the effects on cell migration and proliferation. Human cell lines T98G, A172, 85HG66 and 86HG39 were treated with VPA or left untreated, afterwards Boyden chamber assay was used for measuring vertical migration. In a second assay cells were stimulated to create spheroids and spheroid migration was measured. Proliferation was assessed using a cell counter. VPA decreased proliferation of 86HG39 > A172 > 85HG66 cells, whereas T98G remained uninfluenced. The influence of VPA on migration was different; whereas VPA dose-dependently stimulated migration of 86HG39 cells, migration of T98G and 85HG66 decreased, whereas A172 cells remained uninfluenced. Only 86HG39 and A172 cells created spheroids. In both cell lines Boyden-chamber-findings were confirmed by analysing the influence of VPA on spheroid migration. These non-uniform data demonstrate that the benefit of VPA in glioma treatment is not clear and needs further investigation.

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Intervertebral disc calcification in childhood is rare. Calcifications are discovered by occasion during routine examinations of healthy children or evoke symptoms like neck and shoulder pain or discrete neurological symptoms. The prognosis of nearly all patients is excellent. We report on a 11-year-old girl, who suffered from acute pain in the neck and the left shoulder with increasing paresthesias of her left extremities which led to hospitalisation. Intervertebral disc calcifications were found between several cervical and thoracic vertebra. The only paraclinical finding was an elevated erythrocyte sedimentation rate. After 12 days of conservative and analgetic treatment the clinical condition deteriorated with acute worsening of the neck pain. The MRI revealed a posterior herniation of a calcified disc between the lower cervical spine with spinal cord compression. Immediate neurosurgical intervention led to decompression and disappearance of the symptoms. After 14 months the clinically healthy child only showed the persistence of one intervertebral disc calcification and a complete resolution of the former findings.

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Lipoprotein(a) (Lp(a)) is an independent and inherited risk factor for coronary artery disease. Concentrations of Lp(a) have been widely described in adolescents, but little is known about its concentration in children born small for gestational age (SGA). To assess the influence of intrauterine growth on Lp(a) levels we examined 50 children born SGA and 21 children born adequate for gestational age (AGA). Lp(a) blood levels (mean +/- SD) of the SGA children differed significantly (p < 0.05) from AGA children (22.3 +/- 22.1 vs. 10.9 +/- 7.6 mg/dl). 14 out of 50 adolescents of the SGA group but 1 out of 21 of the AGA group had elevated Lp(a) (>30 mg/dl) concentrations (p < 0.05). These children also had higher triglyceride (1.0 +/- 0.6 mmol/l vs. 0.74 +/- 0.38 mmol/l) levels (p < 0.05) compared to children with Lp(a) levels <30 mg/dl. Adolescents with Lp(a) levels >30 mg/dl showed a significant inverse relation between Lp(a) levels and gestational age (r = -0.68, p < 0. 005). We hypothesize that impairment of fetal growth might influence serum Lp(a) levels in later life.

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OBJECTIVE: The serum concentration of the high-affinity growth hormone-binding protein (GHBP) is increased in obesity but the mechanisms are poorly understood. This study assessed the physiological mechanisms involved in the regulation of GHBP in adiposity. SUBJECTS AND MEASUREMENTS: We tested a number of obesity specific parameters for their association with GHBP. In this study, 199 normal or overweight children and adolescents (101 boys, 98 girls, aged (mean +/- s.d.): 13.7 +/- 2.3 y) underwent an anthropometric evaluation (circumference measurements and bioimpedance analysis) combined with blood withdrawal for the measurement of insulin-like growth factor-I (IGF-I), insulin, leptin and GHBP (by specific RIA), uric acid, triglycerides and cholesterol. RESULTS: By linear regression analysis GHBP correlated significantly (P < 0.001) with percent body fat mass (r = 0.71), waist (r = 0.73) and hip (r = 0.69) circumference, weight (r = 0.61) waist hip ratio (WHR) (r = 0.54), as well as with the serum concentrations of leptin (r = 0.64), uric acid (r = 0.54), insulin (r = 0.45), LDL-cholesterol (r = 0.43), cholesterol (r =0.33), LDL/HDL ratio (r = 0.47), triglycerides (r = 0.30) and with height standard deviations scores (SDS) (r = 0.23). Age, gender and pubertal stage had no impact on GHBP. In a multiple regression analysis containing age and gender, as well as the anthropometric variables, percent fat mass and waist circumference, as independent variables, associations between GHBP and leptin (P < 0.001), cholesterol (P < 0.01), LDL-cholesterol (P = 0.01), LDL/HDL ratio (P = 0.02), triglycerides (P = 0.01) remained significant. In a final model using the stepwise analysis involving age, gender and all the independent predictors of GHBP, waist circumference (P < 0.001), accounted for 49.5% of the 60.0% total variability in GHBP, while the implication of leptin (P < 0.001), age (P < 0.01) and cholesterol (P < 0.05) increased the predicted variability for 7.5%, 1.9%, and 1.0%, respectively. Serum GHBP was significantly reduced in a subgroup of 104 overweight or obese patients during a diet-induced weight loss programme, the coefficient of correlation between GHBP and leptin after (r = 0.45, P < 0.001) and before weight reduction (r = 0.41, P < 0.001) were comparable. CONCLUSION: Waist circumference, an indicator of abdominal body fat mass, is a major determinant of GHBP levels during childhood, while leptin may be one candidate for a signal linking adipocytes to the growth hormone receptor related GHBP release. Additionally, elevated serum levels of GHBP may reflect metabolic disturbances of adiposity.

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The effects of the vasoconstrictor peptide endothelin-1 were examined in the isolated heart during hypoxia, reoxygenation and reperfusion. Isovolumic rat hearts were perfused with Krebs-Henseleit buffer at constant pressure. Cumulative dose-response curves were obtained for endothelin-1 boluses of 0.04 to 400 pmol in five groups of hearts. Coronary flow declined with increasing dosages and was almost abolished at 400 pmol in control hearts. In hearts subjected to mild hypoxia (perfusate PO2 approximately 150 mmHg), the constrictor effect of endothelin-1 was attenuated at moderate dose compared to control hearts (4 vs. 16% flow reduction at 40 pmol; P less than 0.05). The constrictor effect was unaltered in hearts subjected to either 60 min of severe hypoxia (PO2 approximately 35 mmHg) followed by reoxygenation or to 10 min of total ischemia followed by reperfusion (stunning). When hearts were reperfused following 30 min of total ischemia (irreversible injury), the constrictor response to endothelin-1 was potentiated compared to control (e.g. 36 vs. 16% flow reduction at 40 pmol; P less than 0.05). We conclude that endothelin-1 is a potent coronary constrictor in hypoxic, reoxygenated and reperfused heart. The constrictor effect is attenuated during hypoxia, most likely due to the presence of counteracting vasodilator metabolites. During reperfusion, the constrictor effect is unchanged in stunned myocardium, but is augmented in irreversibly injured heart, due to either increased endothelin-1 binding sites or loss of counteracting vasodilator mechanisms such as prostaglandins and/or endothelium-derived relaxing factor.

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Dose-response curves of angiotensin I (AI, 1.0-1000.0 pmol) and angiotensin II (AII, 1.25-1250.00 pmol) were obtained in isolated rat hearts subjected to control conditions, mild hypoxia (PO2 = 145 mm Hg), reoxygenation, ischemic (perfusion pressure = 35 mm Hg) and reperfusion. Both AI and AII caused dose-dependent coronary flow (CF) of 26 +/- 3 and 27 +/- 2%, respectively. The effects of both AI and AII were substantially attenuated during hypoxia, but were fully restored upon reoxygenation. During ischemia, the effect of AII was unaltered while the effect of AI was enhanced compared to the control (P less than 0.05). This enhancement was reversible on reperfusion. Cardiac conversion of AI, calculated from ED50 values for AI and AII, was significantly increased during ischemia (P less than 0.05). Infusion of saralasin (0.5-5.0 micrograms/min) did not increase CF in any of the groups. We conclude that (1) the coronary vasoconstrictive effect of AII is preserved in ischemia but attenuated in hypoxia and (2) cardiac conversion of AI to AII is enhanced in hearts injured by ischemia.

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We examined the effects of the vasoconstrictor peptide endothelin-1 in isolated hearts under ischemic and cardioplegic conditions. Isolated isovolumic rat hearts were perfused with Krebs-Henseleit buffer at constant pressure. Cumulative dose-response curves were obtained for endothelin-1 boluses of 0.04-400 pmol in four groups of hearts. Coronary flow decreased with increasing dosages and was almost abolished at 400 pmol in control hearts perfused at a constant pressure of 100 mm Hg. In hearts made ischemic by reducing coronary perfusion pressure to 35 mm Hg, thus reducing coronary flow by 76%, the constrictor effect of endothelin-1 was well preserved. The endothelin-1 dose-response curve was unaltered when hearts were perfused with buffer containing 30 mM KCl to abolish mechanical activity without reducing extracellular Ca2+ concentration. A fourth group of hearts was perfused with Ca2(+)-free buffer, thus eliminating the source of extracellular Ca2+ as well as mechanical activity. In this group, the constrictor response to endothelin-1 was largely, but not completely, abolished, with a maximal constrictor effect of only 19% as opposed to 87% in control hearts. We conclude that in isolated rat heart endothelin-1 is a potent coronary constrictor under ischemic perfusion conditions and that absence of mechanical activity does not affect the action of endothelin-1, for which the presence of extracellular Ca2+ is essential. The small residual constrictor response with Ca2(+)-free perfusion is probably due to release of Ca2+ from intracellular stores.

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We examined the effects of the vasoconstrictor peptide endothelin-1 in the isolated heart and defined interactions of endothelin-1 with other hormone systems. Isolated isovolumic rat hearts were perfused with Krebs-Henseleit buffer at constant pressure. First, the effect of a single bolus of endothelin-1 (4-400 pmol) was followed for 90 min. The effect of high dosages (40 and 400 pmol) of endothelin-1 on coronary flow was biphasic, with an early vasodilator and a late vasoconstrictor component that was irreversible. Second, cumulative dose-response curves were obtained for endothelin-1 boluses of 0.04-400 pmol. Coronary flow declined with increasing dosages and was almost abolished at 400 pmol. Neither alpha- nor beta-blocking agents (phentolamine and propranolol) nor the Ca2(+)-channel blocker nifedipine altered the effects of endothelin-1, but prostaglandin synthesis inhibition by indomethacin significantly augmented vasoconstriction by endothelin-1. Angiotensin-converting enzyme (ACE) inhibition by captopril antagonized endothelin-1-dependent vasoconstriction to a small extent at 400 pmol. Coronary constriction due to endothelin-1 could not be reversed by nitroglycerin. We conclude that in isolated rat heart endothelin-1 causes marked and long-lasting coronary constriction. The effect is not influenced by sympathetic and Ca2(+)-channel blockade, is enhanced by prostaglandin synthesis inhibition, and is reduced by ACE inhibition.

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