چکیده
A technique for measuring glucose uptake in the small intestine of rabbits was developed. Using this technique, the glucose uptake in the resting jejunum of rabbits and the effect of nicotine infusion on glucose uptake were studied. Experiments were carried out on fasted anaesthetized male rabbits. Four groups of rabbits (6 per group) were studied. A vein draining segment of the upper jejunum was cannulated for blood flow and venous glucose measurements. The left femoral artery and vein were cannulated for arterial blood sampling and drug infusion respectively. Glucose uptake was calculated as a product of jejunal blood flow and the (A-V) glucose difference. The fasting blood glucose levels were 101.0+8.4 mg/dl and 127.0 + 11.3 mg/dl before and after anaesthesia respectively. Basal blood glucose was much higher than this following surgery. The upper jejunum had a resting glucose uptake of 24.1+7.0 mg/min. When nicotine (50ug/kg) was infused intravenously, blood glucose rose from a basal value of 253.8+9.5 mg/dl to 379.8+20.3 mg/dl at the peak of response. Glucose uptake increased to 73.1+11.3 mg/min at the peak of response. These effects of nicotine are mediated through both beta and alpha adrenoceptors. Comparison with previous studies in dogs and rats showed that different adrenoceptors are involved in nicotine hyperglycaemia in fasted dogs, rats and rabbits.
Keywords: Nicotine, rabbit, intestine, glucose uptake, beta-blocker, alpha-blocker.
Résumé
La technique pour mesurer la résorption du glucose dans l’intestin grêle des lapins était développée par l’aide de cette technique. La résorption du glucose au repos dans le jéjunum des lapins et l’effet de l’infusion de la nicotine sur la résorption du glucose étaient étudiées. La veine s’écoulant du segment supérieur était canulé pour avoir d’échantillons du sang artériel et le médicament perfuse. La résorption du glucose était calcule comme le produit de l’écoulement sanguin jéjunal et la différence entre (A-V) en glucose. Les taux du glucose a jeune étaient de 101.0-+8.4 mg/dl et 127.0 ± 11.3mg/dl avant et après l’anesthésie respectivement. Le taux du glucose basal était plus élevé que ceci après la chirurgie. La partie du jéjunum supérieure avait une résorption du glucose au repos de 24.1 ± 7.0 mg/min. Lorsque la nicotine (50 ug/kg) était administre par voie intraveineuse, le taux du glucose s’élevait de la valeur basale de 253.8 ± 9.5mg/min à 379.8 ± 20.3 mg/dl comme effet maximal. La résorption augmentait à 73.1 ± 11.3 mg/min à l’effet maximal. Ces effets de la nicotine sont medies par les adrenocepeurs alpha et beta. Comparant ces résultats avec les études antérieures chez les chiens et les rats, on observait que différent adrenocepeurs sont impliques dans l’hypoglycémie induite par l’administration de la nicotine chez les chiens, rats et lapins a jeune.
Correspondence: Prof. D.D.O. Oyebola, Department of Physiology, College of Medicine, University of Ibadan, Ibadan, Nigeria
مراجع
Grayson J and Oyebola DDO. Effects of catecholamies on intestinal glucose and oxygen uptake in the canine small intestine. J Physiol (Lond) 1985; 343: 311-322.
Grayson J and Oyebola DDO. Effect of nicotine on blood flow, oxygen consumption and glucose uptake in the canine small intestine. Brit J Pharmacol 1985; 85: 797-804.
Alada ARA and Oyebola DDO. Evidence that the gastro-intestinal tract is involved in glucose homeostasis. Afr J Med Med Sci 1996; 25: 243-249.
Alada ARA, Falokun PO and Oyebola DDO. Intestinal glucose uptake in normal, untreated and insulin-treated diabetic dogs. Afr J Med Med Sci 2005; 34: 147-156.
Alada ARA and .Oyebola DDO. The role of adrenergic receptors in the increased glucose uptake by the canine gut. Afr J Med Med Sci 1997; 26: 75-78.
Windmueller HG and Spaeth AE. Identification of ketone bodies and glutamine as the major respiratory fuels in vivo for post-absorptive rat small intestine. J Biol Chem 1978; 253: 69-76.
Potter DE, Moratinos J and Ellis S. Comparative hyperglycaemic responses to norepinephrine, salbutamol and glucagon in normal and alloxan diabetic insulin- controlled rabbits. Arch Int Pharmacodyn Ther 1974; 209: 358-368.
Moratinos J, Potter DE and Ellis S. The influence of propranolol on catecholamine-induced changes in carbohydrate metabolism in the rabbit. Eur J Pharmacol 1975; 32: 186-194.
Knudtzon J. Adrenergic effects on plasma levels of glucagon, insulin, glucose and free fatty acids in rabbits – influences of selective blocking drugs. Acta Physiol Scand 1984; 120: 353 – 361.
Moratinos J, Olmedilla B, de Pablos I and Vigueras MD. Alpha - adrenoceptor involvement in catecholamine-induced hyperglycaemia in conscious fasted rabbits. Br J Pharmacol 1986; 89: 55-66.
Al–Jibouri LM., Furman BL and Parratt JR. Blockade of adrenaline – induced hyperglycaemia in anaesthetized cat by continuous infusion of phentolamine and propranolol. Br J Pharmacol 1980; 68: 461-466.
Kuo SH, Kamara JK and Lum BKB. Adrenergic receptor mechanisms involved in the hyperglycaemia and hyperlacticacidemia produced by sympathomimetic amines in the cat. J Pharmacol Exp Ther 1977; 202: 301-309.
Fleming WW and Kenny AD. The effect of fasting on the hyperglycaemic responses to catecholanies in rats. Br J Pharmacol 1964; 22: 267-274.
Oyebola DDO and Alada ARA. Effects of adrenergic receptor blockers on adrenaline and nicotine-induced hyperglycaemia in the rat. Afr J Med Med Sci 1993; 22: 13-18.
Ajala MO, Oladipo OO, Fasanmade O and Adewole TA. Laboratory assessment of three glucometers. Afr J Med Med Sci 2003; 32: 279-282.
Devreese K and Leroux – Roels G. Laboratory assessment of five glucometers designed for self monitoring of blood glucose concentration. Eur J Clin Chem Clin Biochem 1993; 12: 829-837.
Delaney JP and Custer J. Gastrointestinal blood flow in the dog. Circ Res 1965; 17: 394-402.
Lumley JSP, Green CJ, Lear P and Angell – James JE. In: Essentials of experimental surgery. 1960; Butterworths, London. p31.
Mitruka BM and Rawasley HM. In: Clinical biochemical and haematological reference values in normal experimental animals. Masson. New York. 1977; 102-117.
Tsujimoto A, Tanino S and Kurogochi Y. Effect of nicotine on serum potassium and blood glucose. Jnp J Pharmacol 1965; 15: 415-422.
Milton AS. The effect of nicotine on blood glucose level and plasma non-esterified fatty acid levels in intact and adrenalectomized cats. Br J Pharmacol Chemother 1966; 26: 256-263.
Westfall TC. Tobacco alkaloids and the release of catecholamines: In: Tobacco and related compounds. (Ed) U.S: Von Enler. Pergamon Press. 1965; pp 179-203.
Schiavone MT and Kirpekar SM. Inactivation of secretory responses to potassium and nicotine in the cat adrenal medulla. J Pharmacol Exp Ther 1982; 223: 743-749.
Trendelenburg U. Nicotine and the peripheral autonomic nervous system. In: Tobacco and related compounds. (Ed). U.S. Von Enler. Pergamon, Press. 1965; 167-177.