Role of nitric oxide in glucose-, fructose and galactose-induced increases in intestinal glucose uptake

Previous studies have shown that the infusion of glucose, fructose and galactose resulted in significant increases in intestinal glucose uptake (IGU) and the role of nitric oxide in these responses was not known. The present study was designed to investigate the role of nitric oxide in the observed increases in IGU. Experiments were carried out on thirty-five (35) fasted male anaesthetized Nigerian local dogs divided into seven groups (5 dogs per group). Group I dogs served as control and received normal saline, groups II-IV dogs were infused with glucose (1.1 mg/kg/min), fructose (1.1 mg/kg/min) or galactose (1.1mg/kg/min) while groups V-VII were pretreated with L-Nitro-Arginine-Methyl-Esther (L-NAME) (35 mg/kg) after which they were infused with glucose (1.1 mg/kg/min), fructose (1.1 mg/kg/min) or galactose (1.1mg/kg/min). 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). Blood pressure was recorded continuously. The results showed that pretreatment of the animal with L-NAME, caused significant reductions in jejunal blood flow with complete abolition of glucose-, fructose- and galactose-induced increases in IGU. The results suggest that only glucose-induced IGU was nitric oxide-dependent through the induced hyperemia while the increases in IGU caused by fructose and galactose were not mediated by nitric oxide.Keywords: L-Nitro-Arginine-Methyl-Ester, Hexoses, Haemodynamics, Glucose uptak

Effects of Petrol Exposure on Glucose, Liver and Muscle glycogen levels in the Common African toad Bufo regularis

This study investigated the effects of exposure to petrol on blood glucose, liver and muscle glycogen levels in the common African toad Bufo regularis. A total of 126 adult toads of either sex weighing between 70-100g were used for this study. The experiment was divided into three phases. The phase 1 experiment the acute toxicity test consisted of animals divided into six groups of 10 toads per group and were exposed to water (H2O), H2O + Tween 80, 2ml/l, 3ml/l, 5ml/l, and 10ml/l of petrol respectively for 96 hours using the static renewal bioassay system. In the Phase 2 experiment, the animals were exposed to H2O, H2O + Tween 80, 0.14ml/l, 0.3ml/l, 0.6ml/l, and 1.13ml/l of petrol respectively for 3 days; while in phase 3 experiment they were exposed to petrol solutions for 14 days. After the various exposures, the blood glucose, liver and muscle glycogen contents were determined using standard methods. The results of the study showed that the median lethal concentration of petrol (96 hours LC50) was 4.5ml/l and sub-lethal concentration of petrol caused mortality of animals. Exposure to petrol solutions for 3 days had no significant effect on blood glucose level of the animals but caused significant decrease in the liver and muscle glycogen levels at high concentrations. In the animals exposed to petrol solutions for 14 days, there was a significant increase in glucose levels and significant reduction in liver and muscle glycogen levels at high concentrations when compared with the control. The results show that sub-lethal concentrations of petrol can cause mortality of animals, hyperglycemia and reduction in liver and muscle glycogen levels. The effects of petrol exposure on carbohydrate metabolism depend on the concentration and duration of exposure.Keywords: Petrol, Blood glucose, Liver glycogen, Muscle glycoge

Comparative study of fasting blood glucose and haematological parameters of Wistar rat, Rattus norvegicus and the common African toad, Bufo regularis

Haematological parameters are good indicators of the physiological status of animals and useful in understanding the relationship of blood to the environment. This study was carried out to compare the fasting levels of blood glucose and haematological parameters (Red blood cell count, Packed cell volume, Haemoglobin concentration, White blood cell count, Platelet count, and differential White blood cell counts) in Wistar rats, Rattus norvegicus and the common African toad, Bufo regularis. Ten rats and ten toads were used in the study. The animals were divided into two groups. Group I consists of 10 rats while Group II consists of 10 toads. The animals were fasted overnight before blood samples were collected for the determination of blood glucose and blood parameters. The blood glucose was determined using modified glucose oxidase method while the blood parameters were determined using standard laboratory techniques. The results of the study showed that the fasting blood glucose level in rats was significantly higher than that of toad. The fasting levels of blood parameters, packed cell volume, red blood cell counts, haemoglobin concentration in the toad were significantly lower than those of rats while the white blood cell counts of the toads were significantly higher compared with the rats. There were no significant differences in neutrophil, monocyte, eosinophil and lymphocyte counts of rats when compared with those of the toad

Effects of Telfairia occidentalis leaf extract on plasma lactate and liver glycogen in rats

Summary: Telfairia occidentalis is a green vegetable popularly consumed among the native of Africa and it is generally believed to be of medicinal and nutritional value. Studies have reported its hypoglycaemic and hyperglycaemic effects in rats. In addition to these conflicting reports, the mechanisms for its effects on blood glucose remain inconclusive. The objective of this study was to investigate the mechanism involved in the increased blood glucose following treatment with T. occidentalis. Twenty five (25) male albino rats (200-250g) were randomly divided into 5 groups (n=5/group). Rats in the control group received normal saline while rats in other groups were orally treated with 100 or 200 mg/kg body weight of the extract for either 1 or 2 weeks. At the end of the treatment, the rats were anaesthetized and blood samples were collected for the estimation of some biochemical parameters. The results showed significant decreases in plasma glucose after 1 week of treatment with 100 mg/kg and 200 mg/kg. However, after 2 weeks of treatment with both doses, plasma glucose levels increased significantly and were higher than those of the control and the rats treated for 1 week with both doses. There were also dose- and duration-dependent decreases in glycogen concentration in the treated rats, especially those treated for two weeks. Glucose-6-phosphatase activity and liver glycogen concentration were lower in rats treated for 2 weeks when compared with those treated for 1 week with both doses. Moreover, plasma lactate concentration was lower in the treated groups when compared with control. The results suggest that Telfairia occidentalis-induced lowering of plasma glucose after one week of treatment probably favoured lactate oxidation/gluconeogenesis and elicited breakdown of liver glycogen which resulted in increased plasma glucose after two weeks of treatment.Keywords: Blood glucose, Lactate, Liver glycogen, Glucose-6-phosphatase, Telfairia occidentalisNiger. J. Physiol. Sci. 33(December 2018) 169-17

The haematological effect of telferia occidentals diet preparation

The effects of diet preparation of Telfaria occidentalis   on some haematological indices were carried out on male albino rats. The animals were fed for 4 weeks on diets specially composed to contain 25%, 50% and 57% by weight of the leaf of Telfaria occidentalis . The diet preparations produced a dose-dependent increases in all the measured haematological indices (packed cell volume, heamoglobin concentration red and white blood cell counts). The results confirm the claim that Telfaria occidentalis can be used to cure anaemia

Role of adrenergic receptors in the caffeine-induced increase in glucose uptake by the canine hindlimb

The present study was designed to investigate the effects of alpha and beta adrenergic receptor blockers on caffeine-induced increase in canine hindlimb glucose uptake. The study was carried out on fasted male anaesthetized dogs divided into five groups (5dogs per group). Each dog was given a bolus injection of normal saline, caffeine (6mg/kg) caffeine after pretreatment with prazosin (0.2mg/kg). Caffeine (6mg/kg), caffeine after pretreatment with prazosin (0.2mg/kg), propranolol (0.5mg/kg) or combination of prazosin (0.2mg/kg) and propranolol (0.5mg/kg). The experiments were carried out under resting and exercising conditions of the hindlimb. Hindlimb glucose uptake (HGU) was calculated as the product of blood flow and arterio-venous glucose difference. Blood glucose was determined by the glucose oxidase method and blood flow to the hindlimb was determined by time-collection method. The results showed that pretreatment of the animal with either prazosin or propranolol significantly reduced caffeine-induced hyperglycemia, glucose extraction and hindlimb glucose uptake at rest. The two blockers also separately reduced caffeine-induced hyperglycemia during contraction of the hindlimb. Prazosin or propranolol did not however influence the effect of caffeine on glucose extraction and hindlimb glucose uptake during contraction of the hindlimb. It was therefore concluded that alpha and beta adrenergic receptors are involved in caffeine induced responses at rest and not during hindlimb contraction

Effect of chronic caffeine consumption on cardiac tissue metabolism in the rabbit

Summary: Previous studies on the ability of caffeine to enhance endurance and boost performance have focused on the energy substrates that are utilized by the skeletal muscle and the brain but nothing of such has been reported on cardiac tissue. This study was designed to investigate the effect of caffeine on cardiac tissue metabolism in the rabbit. The study was carried out on adult male New Zealand rabbits divided into 3 groups (n=5). Group I rabbits served as control and were given 0.5ml/Kg of normal saline while group II and III rabbits were administered with 2mg/Kg and 6mg/kg of caffeine respectively for 28 days. Blood samples were collected by retro orbital puncture for biochemical analysis. Animals were sacrificed by cervical dislocation and cardiac tissue biopsies were collected for biochemical and immunohistochemical analysis. Cardiac tissue glycogen concentration was determined by anthrone reagent method. Cardiac tissue CPT 1 activity and cAMP concentration were determined by immunohistochemistry and colorimetry techniques respectively, with assay kits obtained from Biovision Inc. The results showed that Caffeine at 2 and 6 mg/kg significantly inhibited MPO activity from 0.72±0.05 to 0.164±0.045 and 0.46±0.12 U/L respectively (p<0.05). Caffeine at 2mg/kg had no effect on serum nitric oxide but at 6mg/Kg, it significantly increased serum nitric oxide form 28.01±6.53 to 45.25±3.88μM of nitrite (p<0.05). Also, Caffeine at 2 and 6mg/kg increased cardiac tissue glycogen from 15.62±0.73 to 40.69±6.35 and 38.82±6.91mg/100g respectively and carnitine palmytol transferase 1 activity from 18.3 to 20 and 25.2% respectively. In conclusion, the study showed that caffeine consumption increased CPT 1 activity suggesting increased utilization of free fatty acids for energy metabolism and sparing of cardiac tissue glycogen by mechanism(s) which probably involved blockade of A1 adenosine receptors and cAMP signaling pathway.Keywords: Caffeine, Cardiac tissue metabolism, Rabbi

Metabolic fate of the glucose taken up by the intestine during induced hyperglycaemia in dogs

Summary: Available data showed that the intestine increases it glucose uptake in response to hyperglycemia induced by any cause. However, what the intestine does with the glucose is not known. This study investigated the metabolic fate of the glucose taken up by the intestine during hyperglycaemia in dogs. Experiments were carried out on fasted, male, anaesthetized mongrel dogs divided into 4 groups. The control (group 1, n=5) received normal saline (0.2 ml/kg) while groups 2-4 (subdivided into two as low or high dose, n=5 each) received adrenaline (1 μg/kg or 5 μg/kg), glucagon (3 ng/kg or 8 ng/kg) and glucose (10 mg/kg/min or 20 mg/kg/min). Through a midline laparatomy, the upper jejunum was cannulated for Intestinal Blood Flow (IBF) measurement. Blood glucose and lactate levels were determined using glucose oxidase and lactate dehydrogenase methods, respectively. Intestinal Glucose/Lactate Uptake (IGU/ILU) was calculated as the product of IBF and arterio-venous glucose /lactate difference [(A-V) glucose/lactate]. Jejunal tissue samples were obtained for the determination of Glycogen Content (GC) and activities of Glycogen Synthase (GS), Glycogen Phosphorylase ‘a’ (GPa), hexokinase and glucose-6-phosphatase. Anthrone method was used to determine GC while activities of GS, GPa, hexokinase and glucose-6-phosphatase were determined spectrophotometrically. Data were subjected to descriptive statistics and analyzed using student’s t-test and ANOVA at α0.05. Arterial and venous blood glucose and lactate were increased by adrenaline, glucagon and glucose. Venous lactate was higher than arterial lactate in all groups. Intestinal blood flow, (A-V) glucose and (A-V) lactate were increased in all the experimental groups. Intestinal glucose uptake increased by 624% (adrenaline), 705% (glucagon) and 589% (glucose) while intestinal lactate release increased by 422%, 459% and 272% respectively. Intestinal GC increased from 138.72 ± 4.58 mg/100 g to 167.17 ± 4.20 mg/100 g (adrenaline), 229.21 ± 6.25 mg/100 g (glucagon) and 165.17 ± 4.20 mg/100 g (glucose). Adrenaline and glucose had no effect on GS activity but it was increased by glucagon; GPa was decreased while hexokinase activity was increased by adrenaline, glucagon, and glucose. Glucose-6-phosphatase activity was not affected by adrenaline and glucagon but decreased by glucose. The intestine modulates blood glucose levels through lactate formation, glycogen formation and most probably conversion of lactate to glucose through gluconeogenesis.Keywords: Glucose uptake, Lactate uptake, Glycogen, Dog

Effects of Electrical Vagal Stimulation and Bilateral Vagotomy on Bile Flow and Electrolyte Composition in Rats

Effect of electrical vagal stimulation and bilateral vagotomy on the flow and electrolyte composition of bile was studied in fasted and anaesthetized male albino Wistar Rats. Entero-hepatic circulation was maintained artificially by continuous infusion of 1% sodium teurocholate. In each experiment, bile was collected at 15 mins intervals for a period of 90 mins. The bile aliquot was then analyzed for sodium and bircarbonate. The results showed that vagal stimulation significantly increased bile flow and had no effect on the bile concentration of sodium and bicarbonate. Bilateral vagotomy had no significant effect on bile flow, sodium and bicarbonate concentration. The results of this study suggest a very limited role of the vagus nerves in the secretion of bile in the rat.KEYWORDS: Bile flow, Bile electrolytes, Vagotomy, Electrical stimulation