Аннотация
Objectives: Previous study had shown that nicotine acts on blood glucose through release of adrenaline. While there are reports on the hyperglyceic effect of adrenaline in rabbits, there is no information on the effect of adrenaline on intestinal glucose uptake of rabbits. The present study was carried out to find out if adrenaline has any effect on glucose uptake in the rabbit small intestine.
Materials and Methods: Experiments were carried out on fasted anaesthetized male rabbits. Five groups of rabbits (6 rabbits per group) were studied. A vein draining a 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 glucose difference between arterial (A) and venous (V) blood.
Results: The fasting venous blood glucose levels were 151.8+4.4mg/dl and 164.0 + 2.3mg/dl in Groups I and V that were not given adrenoceptor blockers. The upper jejunum had a resting (or basal) glucose uptake of 38.3 + 1.6mg/min in the control group. When adrenaline (2ug/kg) was injected intravenously, arterial blood glucose rose from a basal value of 245.5+4.6mg/dl to 307.5+4.7mg/dl at the peak of response while venous glucose rose from 151.8+4.4mg/dl to 275.8+4.2mg/dl at the peak of response. Glucose uptake increased to 107.4+2.5mg/min at the peak of response. The hyperglycaemic response to adrenaline injection was abolished by propranolol but not by prazosin indicating that this effect of adrenaline is mediated through beta adrenoceptor. Both prazosin and propranolol reduced considerably adrenaline-induced increase in blood flow and glucose uptake, prazosin being more potent in flow reduction.
Conclusion: This study showed that the resting small intestine of rabbits took up large amounts of glucose. The intestinal glucose uptake was markedly increased by adrenaline injection. The response to adrenaline was mediated through alpha and beta adrenoceptors. The responses to adrenaline are different in many respects from those induced by nicotine in rabbits in our earlier study. The reason for the differences is obscure.
Keywords: Adrenaline, rabbit, intestine, glucose uptake, beta-blocker, alpha-blocker
Résumé
Les expériences étaient évaluées sur les lapins males à jeune anesthésiés classés en cinq groupes de six lapins. L’artère et la veine fémorale gauche étaient canulé par prendre un échantillon du sang artériel/veineux et l’infusion du médicament respectivement. L’absorption du glucose était calculée comme produit de l’écoulement du sang jéjunal et la différence entre le sang artériel (A) et veineux (V). Les taux du glucose veineux sanguin à jeune etaient de 151.8+4.4mg/dl et 164.0 + 2.3mg/dl en groupe I et V qui ne recevaient pas des bloqueurs d’adrenocepteurs. Le jéjunum supérieur avait un taux d’absorption au repos de 38.3 + 1.6mg/min chez le groupe de contrôle. Lorsque l’adrénaline (2ug/kg) était injectée par voie intraveineuse, le taux du glucose artériel augmentait de la valeur de base de 245.5+4.6mg/dl à 307.5+4.7mg/dl à la réponse maximale tandis que le glucose veineux augmentait de 151.8+4.4mg/dl à 275.8+4.2mg/dl à la réponse maximal. L’absorption du glucose augmentait de 107.4+2.5mg/min à la réponse maximale. La réponse d’hyperglycémique à l’injection de adrénaline était abolit par le propranolol mais pas par la prazosine indiquant que cet effet de l’adrénaline est medié par les adrenorecepteurs beta. La prazosine et le propranolol réduisaient considérablement augmentation induit par l’adrénaline dans l’écoulement du sang et l’absorption du glucose, prazosine étant plus puissant dans la réduction de l’écoulement. Cette étude démontrait qu’au niveau des intestines greles des lapins au repos s’effectuent une large absorption du glucose. La réabsorption du glucose intestinal était augmentée par l’injection de l’adrénaline. La réponse de l’adrénaline était medié par les adrenorecepteurs alpha et beta. Les réponses à l’adrénaline sont différentes dans plusieurs respects de ceux induits par la nicotine aux lapins dans nos études antérieures. La raison de ces différences est obscure.
Correspondence: Professor D.D.O. Oyebola, Department of Physiology, College of Medicine, University of Ibadan, Ibadan Nigeria.
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