Effect of the beta-adrenergic blockade on intestinal lactate production and glycogen concentration in dogs infused with hexoses.

OBJECTIVES: To investigate effect of beta adrenergic blockade on intestinal lactate production and glycogen concentration in dogs infused with hexoses. METHODS: Experiments were carried out on 35 fasted male anaesthetized dogs weighing between 9 and 16 kg. The animals were divided into 7 (5 dogs per group) groups. Group I dogs served as control and infused with normal saline, groups II-IV were intravenously infused with glucose (1.1 mg/kg/min), fructose (1.1 mg/kg/min) and galactose (1.1 mg/kg/min) respectively while groups V-VII animals were pretreated with propranolol (0.5 mg/kg) and were infused with glucose, fructose or galactose respectively. A vein draining the proximal segment of the jejunum was cannulated along with right and left femoral arteries and veins. Glucose uptake was calculated as the product of jejunal blood flow and the difference between arterial and venous glucose levels (A-V glucose), part of the jejunum tissue was homogenized for estimation of glycogen concentration, and plasma lactate was assayed using lactate colorimetric kit. RESULTS: The result showed significant increase in venous lactate production in response to glucose (78.30 ± 4.57 mg/dL), fructose (60.72 ± 1.82 mg/dL) and galactose (71.70 ± 1.30 mg/dL) when compared with the control group (51.75 ± 1.32 mg/dL) at (p<0.05) with no significant difference in animals pretreated with propranolol. There was no significant difference in glycogen concentration (p>0.05) in animals infused with hexoses only compared with propanolol pretreated group. CONCLUSIONS: Results suggests that one of the possible fates of the enormous amount of glucose taken up by the intestine is conversion to lactate and not glycogen and ß-adrenergic receptor does not affect it.

Acute high blood glucose level attenuates histamine-stimulated acid secretion in male Wistar rats.

BACKGROUND: Studies have shown that the hyperglycemic state induced by intravenous glucagon or glucose infusion may lead to inhibition of gastric acid secretion through the inhibition of gastric vagus activity. Histamine is a well-known mammalian acid secretagogue and it stimulates acid secretion through H2 receptors. Therefore, the aim of this study was to determine what effect an acute hyperglycemic or hypoglycemic state would have on histamine-stimulated acid secretion. METHODS: Male Wistar rats weighing between 200 and 250 g were divided into three groups that received an intravenous infusion of normal saline (control group), glucose (hyperglycemic group), or insulin (hypoglycemic group) followed by injection of histamine to stimulate acid secretion. The oesophageal and duodenal ends of the rats' stomach were cannulated with polythene tubing and the stomach was perfused at room temperature using a Langendoff perfusion apparatus. The effluent was collected in aliquots over 10 min per sample and its pH was measured. RESULTS: There was a significant (p<0.05) decrease in acid secretion following histamine injection in the hyperglycemic rats, while histamine injection led to an increase (p<0.05) in acid secretion in the hypoglycemic rats. CONCLUSIONS: These results show that hyperglycemic state would result in attenuated histamine-stimulated gastric acid secretion, while hypoglycemic state would lead to increased histamine-stimulated gastric acid secretion.

The relaxant actions of ethanolic extract of Tridax procumbens (Linn.) on rat corpus cavernosum smooth muscle contraction.

BACKGROUND: The effect of Tridax procumbens aqueous ethanolic extract on the rat corpus cavernosum smooth muscles was evaluated in the present study. METHOD: Corpus cavernosum strips obtained from healthy, young, adult male Wistar albino rats (250-300 g) were precontracted with phenylephrine (10-7 M) or KCl (60 mM) and then treated with various concentrations of T. procumbens extract (0.15-1.05 mg/mL). The change in corpus cavernosum strip tension was recorded. The interactions between T. procumbens extract with acetylcholine and with sodium nitroprusside were also evaluated. RESULTS: The results indicated that corpus cavernosum strips relaxation induced by T. procumbens extract was concentration-dependent and this was significant (p<0.5). Pre-treatment with a nitric oxide synthase (NOS) inhibitor (N(1) nitro-L-arginine-methyl ester, l-NAME), did not completely inhibit the relaxation. However, T. procumbens extract (0.6 mg/mL) significantly (p<0.5) enhanced both acetylcholine- and sodium nitroprusside-induced corpus cavernosum strips relaxation. CONCLUSIONS: RESULTS suggest that T. procumbens extract has a concentration-dependent relaxant effect on the isolated rat corpus cavernosum. The mechanism of action of T. procumbens extract is complex. A part of its relaxing effect is mediated directly by the release of NO from endothelium which may improve erectile dysfunction.

Calcium-dependent mechanisms mediate the vasorelaxant effects of Tridax procumbens (Lin) aqueous leaf extract in rat aortic ring.

BACKGROUND: Tridax procumbens leaf extract has a folk reputation as an antihypertensive agent in Nigeria. Evidence suggests that it has a relaxant effect on smooth muscles. The present study was designed to investigate the role of calcium in the vasorelaxant effect of this extract. METHODS: Concentration-response studies with noradrenaline (NA), KCl and CaCl2 were carried out in rat aortic rings with and without the extract in physiological salt solution (PSS) (n=6 each). Also, the role of intracellular calcium mobilization was studied by measuring the phasic response to NA in Ca2+-free N,N-ethylene glycol tetraacetic acid (EGTA) PSS (n=6). RESULTS: The results showed that the contractile responses to either NA or KCl were attenuated (p<0.05) in the presence of the extract. Also, the extract attenuated the contractile response to CaCl2 in the presence of NA or KCl (p<0.05) in the Ca2+-free EGTA PSS, while the phasic response to NA was significantly (p<0.05) diminished. CONCLUSIONS: These results suggest that the vasorelaxant effect of T. procumbens leaf extract may be mediated by a non-specific, non-competitive inhibition of Ca2+ influx as well as by inhibition of Ca2+ mobilization from intracellular stores. This implies that it may contain vasorelaxant agents that may have calcium antagonistic potential.