RESUMEN
The aim of this study was to investigate the regional distribution, molecular forms, and gene expression of adrenomedullin in the rat gastrointestinal tract and to examine physiological changes in gastric adrenomedullin after 24-h fasting. The tissue concentration was measured by radioimmunoassay. The molecular forms were analyzed by high performance liquid chromatography. mRNA levels were quantified by Northern blotting and cells positive for adrenomedullin immunoreactivity were localized by immunohistochemistry. A high concentration of adrenomedullin was found in stomach, cecum, and colon (450-520 fmol/g wet tissue). Adrenomedullin immunoreactivity was also detected in duodenum, jejunum, and ileum (200-250 fmol/g wet tissue). Transcripts of the adrenomedullin gene were widely expressed throughout the gastrointestinal tract. The major form of adrenomedullin immunoreactivity in stomach and colon corresponded precisely with authentic adrenomedullin peptide. Adrenomedullin immunoreactive cells were present in the gastrointestinal endocrine system. The concentration and mRNA level of gastric adrenomedullin after fasting were significantly increased compared with findings in controls. Adrenomedullin is ubiquitous in the gastrointestinal tract, and may be produced by endocrine cells. The results suggest that adrenomedullin, through its potent vasodilating activity, may play some role, in the stomach including the regulation of the mucosal blood flow.
Asunto(s)
Fenómenos Fisiológicos del Sistema Digestivo , Mucosa Gástrica/metabolismo , Mucosa Intestinal/metabolismo , Péptidos/genética , Péptidos/metabolismo , Adrenomedulina , Animales , Técnicas de Cultivo , Ayuno/fisiología , Expresión Génica , Inmunohistoquímica , Masculino , ARN Mensajero/análisis , Ratas , Ratas Sprague-Dawley , Valores de ReferenciaRESUMEN
Adrenomedullin (AM), a novel hypotensive peptide, is suggested to be involved in defense mechanisms against hypertension, however, the detail mechanisms have not been clarified. To elucidate whether AM synthesis would be altered in a salt dependent hypertension, we have investigated the AM concentration and AM messenger RNA (mRNA) level in tissues of Dahl salt-sensitive rats on either low- or high-salt intake. The AM concentration in cardiac ventricle of the high-salt group was significantly higher than that of the low-salt group. The plasma AM concentration was also significantly higher in the high-salt group than in the low-salt group. Furthermore, the plasma AM concentration correlated well with the weight of left ventricle. RNA blot analysis revealed that the AM mRNA level in cardiac ventricle of the high-salt group was higher than that of the low-salt group. These results suggest that AM participates in the pathophysiology of salt dependent hypertension and plays a role in cardiac hypertrophy.
Asunto(s)
Hipertensión/metabolismo , Miocardio/metabolismo , Péptidos/análisis , ARN Mensajero/análisis , Cloruro de Sodio Dietético/administración & dosificación , Adrenomedulina , Animales , Hipertensión/inducido químicamente , RatasRESUMEN
Proadrenomedullin N-terminal 20 peptide (PAMP) is a novel hypotensive peptide processed from an adrenomedullin precursor. In this study, high concentrations of immunoreactive PAMP (ir-PAMP) were detected in rat cardiac atrium and adrenal gland by the radioimmunoassay (RIA) for rat PAMP. The mean plasma concentration of rat ir-PAMP was 3.8 +/- 0.3 fmol/ml. Analysis in atrium, adrenal gland and plasma with high performance liquid chromatographies showed that most ir-PAMP emerged as one major peak at the position exactly identical to that of the authentic rat PAMP. We further investigated the tissue and plasma concentrations of rat ir-PAMP in spontaneously hypertensive rat (SHR) to elucidate the role of PAMP in hypertension. The ir-PAMP concentration in heart tissue of SHR was found to be increased compared with that of the control rat. Especially, the atrial concentration of ir-PAMP of SHR (5.66 +/- 0.78 fmol/mg wet tissue) was significantly higher than that of the control (3.29 +/- 0.22 fmol/mg wet tissue). Cardiac PAMP might have a role for the protection from systemic hypertension.
Asunto(s)
Glándulas Suprarrenales/química , Atrios Cardíacos/química , Fragmentos de Péptidos/análisis , Péptidos , Proteínas/análisis , Radioinmunoensayo/métodos , Adrenomedulina , Secuencia de Aminoácidos , Animales , Humanos , Hipertensión/sangre , Hipertensión/metabolismo , Datos de Secuencia Molecular , Especificidad de Órganos , Fragmentos de Péptidos/síntesis química , Proteínas/síntesis química , Ratas , Ratas Endogámicas SHR , Ratas Sprague-Dawley , Ratas Wistar , Sensibilidad y EspecificidadRESUMEN
Adrenomedullin (AM) is a novel hypotensive peptide originally isolated from the pheochromocytoma tissue of humans. To examine the pathophysiological role of AM in primary aldosteronism (PA), the plasma concentration of AM in patients with PA was measured with a specific radioimmunoassay and compared to that in age- and sex-matched healthy normotensive subjects. In addition, the concentrations of AM as well as catecholamines in the plasma from both the adrenal vein and the inferior vena cava (IVC) were measured to determine whether or not the circulating AM in these PA patients is supplied from the adrenal medulla, which contains a much higher concentration of AM than any other human tissue does. The plasma concentration of AM in the PA patients (4.57 +/- 0.32 fmol/mL, n = 6) was significantly (P < .01) higher than that in the healthy subjects (3.06 +/- 0.20 fmol/mL, n = 12). A significant positive correlation (r = 0.62, P < .01) was observed between the mean blood pressure and the plasma AM level. The AM concentration in plasma from the adrenal vein was almost the same level as that from the IVC although the concentrations of both epinephrine and norepinephrine in the adrenal vein were much higher than those in the IVC. Therefore, it seems unlikely that the plasma AM in the PA patients is mainly supplied from the adrenal medulla. Judging from the potent hypotensive activity of AM, the present findings suggest that AM participates in defense mechanisms acting against the elevation of blood pressure in the patients with PA.
Asunto(s)
Hiperaldosteronismo/sangre , Péptidos/sangre , Glándulas Suprarrenales/irrigación sanguínea , Adrenomedulina , Femenino , Humanos , Hiperaldosteronismo/complicaciones , Hipertensión/sangre , Hipertensión/etiología , Masculino , Persona de Mediana Edad , Concentración Osmolar , Péptidos/fisiología , Radioinmunoensayo , Venas , Vena Cava InferiorRESUMEN
Adrenomedullin is a strong vasorelaxing peptide discovered in pheochromocytoma tissue. Monocrotaline, a pyrrolizidine alkaloid derived from Crotalaria spectabilis, is known to cause pulmonary hypertension. To test the hypothesis that adrenomedullin plays a role similar to that of atrial natriuretic peptide or brain natriuretic peptide in modulating right ventricular responses to pulmonary hypertension, we have compared concentrations of immunoreactive rat adrenomedullin and adrenomedullin messenger RNA levels in tissues of monocrotaline treated rats with those of control rats. We also measured the effect of pulmonary hypertension on plasma level of the peptide. The concentrations of adrenomedullin immunoreactivity in right ventricle and plasma were significantly higher in monocrotaline treated rats than in control rats. The messenger RNA level of adrenomedullin in right ventricle was also higher in monocrotaline treated rats than in control rats. These results suggest that adrenomedullin participates in the mechanism to counteract the high blood pressure in pulmonary circulation.
Asunto(s)
Hipertensión Pulmonar/metabolismo , Miocardio/metabolismo , Péptidos/metabolismo , Adrenomedulina , Animales , Modelos Animales de Enfermedad , Ventrículos Cardíacos/química , Hipertensión Pulmonar/sangre , Hipertensión Pulmonar/inducido químicamente , Immunoblotting , Pulmón/efectos de los fármacos , Pulmón/metabolismo , Masculino , Monocrotalina/toxicidad , Péptidos/sangre , Péptidos/inmunología , ARN/análisis , ARN Mensajero/metabolismo , Radioinmunoensayo , Ratas , Ratas Sprague-Dawley , Valores de Referencia , Función Ventricular Derecha/fisiologíaRESUMEN
Adrenomedullin is a new bioactive peptide recently isolated from pheochromocytoma. We report on the rat adrenomedullin distribution and molecular forms in various tissues and plasma. Using a sensitive radioimmunoassay system for rat adrenomedullin, high concentrations of immunoreactive rat adrenomedullin were detected in adrenal gland, lung and cardiac atrium. In lung and atrium, the immunoreactivity concentration in rat was about 6-10 times higher than that in human. The mean plasma concentration of immunoreactive rat adrenomedullin was 3.60 +/- 0.34 fmol/ml (mean +/- S.D.). Analysis in adrenal gland, lung and atrium with reverse-phase and gel-filtration high-performance liquid chromatography showed that most immunoreactive rat adrenomedullin emerged as a single peak at a position exactly identical to that of the authentic rat adrenomedullin peptide, synthesized according to the sequence predicted from the cDNA.
Asunto(s)
Glándulas Suprarrenales/química , Atrios Cardíacos/química , Pulmón/química , Péptidos/análisis , Péptidos/sangre , Adrenomedulina , Animales , Humanos , Peso Molecular , Especificidad de Órganos , Péptidos/síntesis química , Péptidos/química , Radioinmunoensayo , RatasRESUMEN
Adrenomedullin is a new hypotensive peptide recently identified in human pheochromocytoma arising from adrenal medulla. We report here the cDNA encoding a rat adrenomedullin precursor. The precursor is 185 amino acids in length, including a 21 residue putative signal peptide at the N-terminus. Rat adrenomedullin consists of 50 amino acids similar to, but distinct from human adrenomedullin; 2 residues were deleted and 6 residues were substituted compared to those in the human peptide. In the proadrenomedullin N-terminal 20 peptide, whose amino acid sequence is present in adrenomedullin precursor, 3 amino acids were substituted. RNA blot analysis showed that rat adrenomedullin mRNA was expressed in adrenal glands, lung, kidney, heart, spleen, duodenum and submandibular glands. Synthetic rat adrenomedullin elicits a potent and long-lasting hypotensive activity in anesthetized rats.