Effects Of Caffeine And Ethanolic Extract Of Kolanut On Glucose Uptake In The Canine Hindlimb At Rest And During Contraction

Summary: The study investigated the effects of caffeine and ethanolic extract of kolanut (EEK) on glucose uptake in the canine hindlimb at rest and during contraction. Thirty male anaesthetized Mongrel dogs (11 - 13kg) were divided into six groups (5dogs/group). Caffeine (6mg/kg), EEK (5mg/kg), or normal saline (control) was administered intravenously to each group at rest. Arterial and venous blood samples were collected at 0, 5, 10, 15, 20, 25, 30, 45, 60, 75 and 90 minutes after drug administration. Blood glucose was measured by glucose oxidase method. Arterio-venous (A-V) glucose difference was calculated and venousblood flow (VBF) was measured during the sampling period. Hindlimb Glucose Uptake (HGU) was calculated as the product of (A-V) glucose and blood flow. After sampling at rest, the experiments were repeated with the right femoral nerve stimulated using electrical stimulator at 5Hz. At rest, (A-V) glucose increased significantly (

The role of alpha and beta adrenergic receptors in cortisol-induced hyperglycaemia in the common African toad (Bufo regularis)

The role of adrenergic receptors in cortisol-induced hyperglycaemia is not well known. The present study investigates the effects of adrenergic receptor blockers in cortisol-induced hyperglycaemia in the common African toad (Bufo regularis). Each toad was fasted and anesthetized with sodium pentobarbitone (3 mg/100 g i.p). The animals (control) received intravenous (i.v) injection of 0.7% amphibian saline while animals (untreated) were given cortisol (20 μg/kg). In pre-treatment groups, animals received prazosin (0.2 mg/kg i.v), propranolol 0.5 mg/kg or combination of prazosin (0.2 mg/kg i.v) and propranolol (0.5 mg/kg i.v) before i.v injection of cortisol (20 μg/kg). Thereafter, blood samples were collected for estimation of blood glucose level using the modified glucose oxidase method. Cortisol caused significant increase in blood glucose level from 44.4±3.8 to 71.7±9.7 mg/dl. Pretreatment of the toads with propranolol (0.5 mg/kg i.v) caused significant reduction (p≤ 0.01) in cortisolinduced hyperglycaemia while pre-treatment with prazosin (0.2 mg/kg i.v) produced no significant effect on hyperglycaemia induced by cortisol. The combination of both prazosin and propranolol completely abolished the effects of cortisol on blood glucose level. The results suggest that cortisol-induced hyperglycaemia in the toad (B. regularis) is mediated probably by both the α- and β-adrenergic receptors with the beta adrenergic receptors playing dominant role.Keywords: Cortisol, hyperglycaemia, prazosin, propranolol, amphibian saline, common African toad.African Journal of Biotechnology Vol. 12(36), pp. 5554-555

Role of Adrenergic Receptors in Glucose, Fructose and Galactose-Induced Increases in Intestinal Glucose Uptake in Dogs

The study investigated the role of adrenergic receptors in glucose, fructose-, and galactose- induced increases in intestinal glucose uptake. Experiments were carried out on fasted male anaesthetized Nigerian local dogs divided into seven groups (with five dogs per group). Group I dogs were administered normal saline and served as control. Dogs in groups II, III and 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. Another three groups, V, VI and VII were pretreated with prazosin (0.2mg/kg), propranolol (0.5mg/kg) or a combination of prazosin (0.2mg/kg) and propranolol (0.5mg/kg) followed by glucose infusion, frutose infusion or galactose infusion respectively. Through a midline laparatomy, the upper jejunum was cannulated for blood flow measurement and blood samples were obtained for measurement of glucose content of the arterial blood and venous blood from the upper jejunal segment. Glucose uptake was calculated as the product of jejunal blood flow and the difference between arterial and venous glucose levels (A-V glucose). The results showed that pretreatment of the animal with prazosin had no effect on glucose and galactose induced increases in glucose uptake. However, pretreatment with propranolol completely abolished glucose, fructose and galactose-induced increases in intestinal glucose uptake. Prazosin also significantly reduced galactose-induced increase in intestinal glucose uptake. The results suggest that the increases in intestinal glucose uptake induced by glucose and fructose are mediated mostly by beta adrenergic receptors while that of galactose is mediated by both alpha and beta adrenergic receptors.Keywords: Hexoses administration, Adrenergic receptors, Glucose uptake, Dog

Influence of nitric oxide on histamine and carbachol – induced gastric acid secretion in the common African toad – Bufo regularis

The study aimed to determine the influence of nitric oxide (NO) on the action of histamine and carbachol on acid secretion in the common African toad – Bufo regularis. Gastric acidity was determined by titration method. The acid secretion was determined when nitric oxide was absent following administration of NO synthase inhibitor; N-nitro-L-arginine methyl ester (L-NAME) and when nitric oxide was in excess by administration of exogenous NO donor, sodium nitroprusside (SNP). Histamine or carbachol increased acid secretion in the toad. Acid output increased from 0.32 ± 0.04 mEq/15min to 0.56 ± 0.08 and 0.61 ± 0.05 mEq/15min for histamine and carbachol respectively (P < 0.05). Pretreatment of the toad with L-NAME produced further increases in histamine (0.62 ± 0.06 mEq/15min) or carbachol (0.74 ± 0.06 mEq/15min) induced acid secretion respectively. SNP however, completely abolished the acid secretion stimulated by either histamine or carbachol. It was therefore concluded that nitric oxide has a negative influence on the histamine or carbachol – stimulated acid secretion in the toad – Bufo regularis.Keywords: nitric oxide, histamine, carbachol, acid secretion Nigerian Journal of Physiological Sciences Vol. 20(1&2) 2005: 74-7

The Aqueous Calyx Extract of Hibiscus sabdariffa Lowers Blood Pressure and Heart Rate via Sympathetic Nervous System Dependent Mechanisms

Summary: The antihypertensive effect of Hibiscus sabdariffa (HS) has been validated in animals and man. This study tested the hypothesis that its hypotensive effect may be sympathetically mediated. The cold pressor test (CPT) and handgrip exercise (HGE) were performed in 20 healthy subjects before and after the oral administration of 15mg/Kg HS. The blood pressure (BP) and heart rate (HR) responses were measured digitally. Mean arterial pressure (MAP; taken as representative BP) was calculated. Results are expressed as mean ±SEM. P&lt;0.05 was considered significant. CPT without HS resulted in a significant rise in MAP and HR (111.1±2.1mmHg and 100.8±2.0/min) from the basal values (97.9±1.9mmHg and 87.8±2.1/min; P&lt;0.0001 respectively). In the presence of HS, CPT-induced changes (ΔMAP=10.1±1.7mmHg; ΔHR= 8.4±1.0/min) were significantly reduced compared to its absence (ΔMAP= 13.2±1.2mmHg; ΔHR= 13.8±1.6/min; P&lt;0.0001 respectively). The HGE done without HS also resulted in an increase in MAP and HR (116.3±2.1mmHg and 78.4±1.2/min) from the basal values (94.8±1.6mmHg and 76.1±1.0/min; p&lt;0.0001 respectively). In the presence of HS the HGE-induced changes (ΔMAP= 11.5±1.0mmHg; ΔHR= 3.3±1.0/min) were significantly decreased compared to its absence (ΔMAP=21.4±1.2mmHg; ΔHR= 12.8±2.0/min; P&lt;0.0001 respectively). The CPT and HGE -induced increases in BP and HR suggest Sympathetic nervous system activation. These increases were significantly dampened by HS suggesting, indirectly, that its hypotensive effect may be due to an attenuation of the discharge of the sympathetic nervous system.Keywords: Hibiscus sabdariffa, Cold pesssor test, Hand grip exercise, Blood pressure, Heart rat

The role of adrenergic receptors in nicotine-induced hyperglycemia in the common African toad (Bufo regularis)

The role of adrenergic receptors in nicotine-induced hyperglycaemia has not been well studied in amphibians. Thus, this study investigates the effects of alpha and beta adrenergic receptor blockers in nicotine-induced hyperglycaemia in the common African toad Bufo regularis. Toads fasted for 24 h were anaesthetized with sodium pentobarbitone (3 mg/100 g body weight) intraperitoneally (i.p) and given intravenous (i.v) injection of 0.7% amphibian saline, or nicotine (50 µg/kg), nicotine(50 µg/kg i.v) 30 min after pretreatment with prazosin (0.2 mg/kg i.v), propranolol (0.5 mg/kg i.v) or combination of both prazosin (0.2 mg/kg i.v) and propranolol (0.5 mg/kg, i.v). Thereafter, blood samples were also collected from truncus arteriosus for estimation of blood glucose level using the modified glucose oxidase method. Nicotine caused significant increase (P&lt;0.01) in the levels of blood glucose in the common African toad. Pre-treatment of the toads with prazosin (0.2 mg/kg i.v) or propranolol (0.5 mg/kg, i.v) significantly (p &lt; 0.01) reduced the hyperglycaemia induced by nicotine (50 µg/kg i.v). However, the combination of prazosin (0.2 mg/kg i.v) and propranolol (0.5 mg/kg, i.v) abolished the hyperglycaemic effect of nicotine (50 µg/kg i.v). The above results on glucose metabolism suggests involvement of both alpha and beta adrenoceptors in nicotine-induced hyperglycaemia in common African toad B. regularis.Keywords: Nicotine, hyperglycaemia, prazosin, propranolol, common African toad Bufo regularis.African Journal of Biotechnology, Vol 13(30) 3101-310