Abstract P068: Comparison Effects of Leptin and Phentolamine on Cardiovascular System

Abstract

Background: Leptin participates not only in negative feedback control of body adiposity but in cardiovascular and sympathetic regulations. The aim of this research is to study the acute effects of leptin on cardiovascular system. Rabbits were used as experimental animals. Materials and Methods: Blood pressure and EKG have been recorded at basal and after injection of these medications. Intravenous bolus of 500μg/kg of leptin has been injected into marginal vein in first group (15 rabbits), whereas second group (15 rabbits), has been injected α-adrenergic receptor antagonist phentolamine (0.01 mg/kg). Results: First group of animals received IV leptin 500 microgram/kg, there was significant increase in mean arterial blood pressure from 75.60±0.61 mmHg to 94.63±0.51 mmHg (P<0.001). Moreover, heart rate has been increased after IV leptin, from 225±3.04 beat/min to 291±4.42 beat/min (P<0.001). Second group of animals received phentolamine significantly decreased response of cardiovascular action of leptin. Leptin increased blood pressure nonsignificantly. Mean arterial blood pressure was before treatment 74.70±0.51 mmHg and became after treatment with phentolamine and leptin in sequences 77.63±0.41 mmHg (P>0.05). However, phentolamine did not impair effects of leptin on heart rate. Heart rate was 229±2.41 beat/min and significantly increased after treated with phentolamine and leptin in sequences 344±3.52 beat/min (P<0.001). This study elucidated significant positive relationship between blood pressure and heart rate in group which is treated with leptin (p<0.001), but this relationship was inversely significant related in group two which is treated with phentolamine (p<0.001). Conclusions: These results suggest that intravenous injection of leptin causes increases in arterial blood pressure and heart rate in anesthetic rabbits, and these effects could be opposed by adrenergic blockade. This may be partially explained by the effect of leptin on cardiovascular system could be mediated by sympathetic pathway.