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Extracts of Persea americana Mill (Lauraceae) ("Avocado") have been traditionally used to treat hypertension and diabetes mellitus. Accordingly, we studied the hypoglycaemic and renal function effects of P. americana leaf ethanolic extracts (PAE) in STZ-induced diabetic rats. Oral glucose tolerance responses to various doses of PAE were monitored in fasted rats following a glucose load. Rats treated with deionized water or standard hypoglycaemic drugs acted as untreated and treated positive controls, respectively. Acute renal effects of PAE were investigated in anesthetized rats challenged with 0.077 M NaCl after a 3.5-h equilibration for 4 h comprising 1 h control, 1.5 h treatment and 1.5 h recovery periods. PAE was added to the infusate during the treatment period. Hepatic glycogen concentration was measured after 6 weeks of daily treatment with PAE. PAE induced dose-dependent hypoglycaemic responses in STZ-induced diabetic rats while subchronic PAE treatment additionally increased hepatic glycogen concentrations. Acute PAE infusion decreased urine flow and electrolyte excretion rates, whilst subchronic treatment reduced plasma creatinine and urea concentrations. These results indicate not only the basis of the ethnomedicinal use of P. americana leaf extract in diabetes management, but also of need for further studies to identify and evaluate the safety of PAE's bioactive compounds.

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Studies in our laboratories suggest that Sclerocarya birrea stem-bark ethanolic extract (SBE) has hypoglycemic properties. Accordingly, we investigated the effects of SBE on major complications of diabetes mellitus; blood glucose, renal function and mean arterial blood pressure (MAP) in non-diabetic and STZ-induced diabetic rats. Oral glucose tolerance test responses to various SBE doses (60, 120 and 240 mg kg(-1)) were studied in fasted rats following glucose load (0.86 g kg(-1), p.o.). Rats treated with deionized water (3 ml kg(-1) p.o.), or standard hypoglycemic drugs (insulin, 100 microg kg(-1), s.c.; metformin, 500 mg kg(-1), p.o. or glibenclamide, 500 microg kg(-1), p.o) acted as untreated and treated positive controls, respectively. Blood was collected in non-diabetic rats after 45 min of SBE, metformin or glibenclamide for plasma insulin determination. Acute SBE effects on renal function and MAP were studied in anesthetized rats challenged with hypotonic saline after 3.5h equilibration for 4h of 1h control, 1.5h treatment and 1.5h recovery periods. SBE was added to the infusate during the treatment period. Chronic effects were monitored for 5 weeks in animals daily treated with SBE (120 mg kg(-1) p.o.) while hepatic glycogen concentration was measured at the end of the experimental period. SBE exhibited dose-dependent reduction in blood glucose concentration. SBE and metformin did not affect plasma insulin secretion in non-diabetic rats, while glibenclamide increased plasma insulin concentration. The hypoglycemic effect of SBE treatment was associated with increased hepatic glycogen synthesis. Acute SBE administration did not significantly alter kidney function, but chronic SBE treatment for decreased plasma urea and creatinine concentrations of STZ-diabetic rats with concomitant increase in GFR by comparison with control rats at the corresponding period (0.7+/-0.2 vs. 1.4+/-0.3 ml min(-1)). SBE treatment reduced blood pressure in all groups of animals. The observations suggest that SBE has reno- and cardio-protective effects in diabetes mellitus. The current results indicate the basis for SBE use as complementary remedy in diabetes.

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The aim of this study was to examine some in vivo and in vitro cardiovascular effects of Helichrysum ceres leaf ethanolic extract (HCE) in experimental animal paradigms. The acute effects of HCE on blood pressure were studied in anaesthetised normotensive male Wistar rats challenged with intravenous hypotonic saline infusion after a 3.5-hour equilibration for four hours of one-hour control; 1.5-hour treatment and 1.5-hour recovery periods. HCE was added to the infusate during the treatment period. Sub-chronic hypotensive effects of HCE were examined in weanling Dahl Salt-sensitive (DSS) genetically hypertensive rats; which progressively develop hypertension with age; treated with HCE (80 mg / kg) every third consecutive day for seven weeks. isolated atrial muscle strips; portal veins and descending thoracic aortic rings of healthy normotensive Wistar rats were used to investigate the vascular effects of HCE. Acute HCE administration caused a significant (p 0.05) fall in blood pressure in the normotensive anaesthetised Wistar rats. DSS hypertensive rats treated with HCE displayed low arterial blood pressure and heart rate values from weeks five to seven. HCE produced concentration-dependent negative inotropic and chronotropic effects on rat isolated electrically driven left; and spontaneously beating right atrial muscle preparations; respectively. HCE also evoked concentration-dependent relaxation responses of endothelium-intact aortic rings and portal veins isolated from healthy normotensive Wistar rats. The vasorelaxant effects of HCE in intact aortic rings were significantly reduced; but not completely abolished by adding endothelial-derived factor (EDRF) inhibitor; L-NAME; suggesting that the vasorelaxant effect of the extract is mediated via EDRF-dependent and independent mechanisms. The results of the study suggest that the hypotensive action of HCE is elicited; in part; directly by decreasing myocardial contractile performance and total peripheral vascular resistance due to its negative inotropic and chronotropic effects on rat isolated atrial muscle strips; and vasorelaxant effects on isolated vascular smooth muscles. The observed cardiovascular effects of HCE partly support the basis for its use in the management of high blood pressure in folkloric medicine

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Previous observations indicate that Ficus thonningii (Blume) [Moraceae] stem-bark extracts may be useful in the control of diabetes mellitus. Accordingly, we investigated in some experimental animal paradigms the effects of F. thonningii stem-bark ethanolic extract (FTE) on renal and cardiovascular functions as complications of diabetes. Oral glucose tolerance tests were conducted in separate groups of non-diabetic and STZ-treated diabetic rats given glucose load (0.86 g x kg(-1), p.o.) after 18-h fast, followed by various FTE doses (60, 120, and 240 mg x kg(-1)). Rats treated with deionized water (3 mL x kg(-1) p.o.), or metformin (500 mg x kg(-1) p.o.) acted as untreated and treated positive controls, respectively. Blood glucose was monitored at 15-min intervals for the first hour, and hourly thereafter for 3 h. Acute effects of FTE on kidney function and mean arterial blood pressure (MAP) were investigated in anaesthetized rats challenged with hypotonic saline after a 3.5-h equilibration for 4 h of 1 h control, 1.5 h treatment, and 1.5 h recovery periods. FTE was added to the infusate during the treatment period. Chronic effects of FTE were studied in individually caged rats treated daily with FTE (120 mg x kg(-1), p.o.) for five weeks. Cytotoxicity of FTE was assessed by dye-reduction colorimetric (MTT) assay on MDBK and LLCPK1 kidney cell lines exposed for 24 h, 48 h, and 72 h to graded concentrations of the extract. Myocardial contractile performance was evaluated on rat isolated atrial muscle strips. FTE, like metformin, decreased blood glucose levels in non-diabetic and STZ-diabetic rats. Both acute and chronic FTE treatments did not affect renal function. In vitro studies demonstrated that FTE increased MDBK cell metabolic activity by an average of 15% (72 h), and LLCPK1 mirrored the controls. Acute intravenous infusion of FTE reduced the MAP from 119 +/- 1 mmHg to 98 +/- 4 mmHg. The MAP also was reduced throughout the five-week experimental study period. FTE also produced concentration-dependent, negative inotropic and chronotropic effects on rat isolated, electrically driven left-, and spontaneously beating right-, atrial muscle preparations. Our experimental findings suggest that FTE possesses reno- and cardio-protective effects in diabetes mellitus.

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The cardiovascular effects of Persea americana Mill (Lauraceae) aqueous leaf extract (PAE) have been investigated in some experimental animal paradigms. The effects of PAE on myocardial contractile performance was evaluated on guinea pig isolated atrial muscle strips, while the vasodilatory effects of the plant extract were examined on isolated portal veins and thoracic aortic rings of healthy normal Wistar rats in vitro. The hypotensive (antihypertensive) effect of the plant extract was examined in healthy normotensive and hypertensive Dahl salt-sensitive rats in vivo. P americana aqueous leaf extract (25-800 mg/ml) produced concentration-dependent, significant (p < 0.05-0.001), negative inotropic and negative chronotropic effects on guinea pig isolated electrically driven left and spontaneously beating right atrial muscle preparations, respectively. Moreover, PAE reduced or abolished, in a concentration-dependent manner, the positive inotropic and chronotropic responses of guinea pig isolated atrial muscle strips induced by noradrenaline (NA, 10(-10)-10(-5) M), and calcium (Ca(2+), 5-40 mM). PAE (50-800 mg/ml) also significantly reduced (p < 0.05-0.001) or abolished, in a concentration-dependent manner, the rhythmic, spontaneous, myogenic contractions of portal veins isolated from healthy normal Wistar rats. Like acetylcholine (ACh, 10(-8)-10(-5) M), the plant extract (25- 800 mg/ml) produced concentration-related relaxations of isolated endothelium-containing thoracic aortic rings pre-contracted with noradrenaline. The vasorelaxant effects of PAE in the isolated, endothelium-intact aortic rings were markedly inhibited or annulled by N(G)-nitro-L-arginine methyl ester (L-NAME, 10(-5) M), a nitric oxide synthase inhibitor. Furthermore, PAE (25-400 mg/kg iv) caused dose-related, transient but significant reductions (p < 0.05-0.001) in the systemic arterial blood pressure and heart rates of the anaesthetised normotensive and hypertensive rats used. The results of this laboratory animal study indicate that PAE caused bradycardia, vasorelaxation and hypotension in the mammalian experimental models used. The vasorelaxant action of PAE was endothelium dependent, and was, therefore, possibly dependent on the synthesis and release of nitric oxide (NO). The vasorelaxant effects of PAE appeared to contribute significantly to the hypotensive (antihypertensive) effects of the plant extract. However, the findings of this study tend to suggest that P americana leaf could be used as a natural supplementary remedy in essential hypertension and certain cases of cardiac dysfunctions in some rural Africa communities.

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This study was undertaken to investigate some cardiovascular effects of Hypoxis hemerocallidea Fisch & CA Mey (Hypoxidaceae) corm (African potato) aqueous extract in experimental animal paradigms. The effect of the corm aqueous extract (APE) on myocardial contractile performance was evaluated on guinea-pig isolated atrial muscle strips in vitro; whereas the antihypertensive (hypotensive) effect of the plant extract was examined in hypertensive Dahl salt-sensitive rats in vivo. APE (25-400 mg/ml) produced concentration-dependent, significant (p < 0.05-0.001) negative inotropic and negative chronotropic effects on guinea-pig isolated electrically driven left, and spontaneously beating right atrial muscle preparations, respectively. Moreover, APE reduced or abolished, in a concentrationdependent manner, the positive inotropic and chronotropic responses of guinea-pig isolated atrial muscle strips induced by noradrenaline (NA, 1-100 microM) and calcium (Ca2+, 5-40 mM). The negative inotropic and chronotropic effects of APE on guinea-pig atrial muscle strips were not modified by exogenous administration of atropine (ATR, 7.5 x 10(-7)-2.5 - 10(-6) M) to the bath fluid. APE also significantly reduced (p < 0.05-0.001) or abolished in a concentration-dependent manner, the rhythmic, spontaneous, myogenic contractions of portal veins isolated from rats. Furthermore, APE caused dose-related transient but significant (p < 0.05-0.001) reductions in the systemic arterial blood pressure and heart rates of the hypertensive rats used. Although the exact mechanisms of the cardiodepressant and the transient hypotensive (antihypertensive) actions of APE could not be established in the present study, we exclude the involvement of the cholinergic system; since the extract's cardiovascular effects were resistant to atropine pretreatment. However, the results of this laboratory animal study indicated that APE caused bradycardia and brief hypotension in the mammalian experimental models used. These observations tend to suggest that the herb may be used as a natural supplementary remedy in some cases of cardiac dysfunctions and in essential hypertension. The findings of this experimental animal study lend pharmacological support to the folkloric, anecdotal uses of the African potato in the management and/or control of certain cardiac dysfunctions and essential hypertension in some rural communities of southern Africa.

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