Abstract
The incretin hormone, glucagon-like peptide-1 (GLP-1), is known for responding to dietary fat and carbohydrate. It elicits effects on pancreas, gut, and brain to stabilize blood glucose levels. We have previously reported that the GLP-1 agonist, exenatide, vasodilates the kidney and suppresses proximal reabsorption. The present study was undertaken to determine whether the renal effects of exenatide are mediated by nitric oxide (NO) and/or prostaglandins. Inulin clearance (glomerular filtration rate, GFR) and urine flow rate (UV) were measured in anesthetized rats before and during exenatide infusion (1 nmol/h iv). Animals were pretreated with cyclooxygenase (COX) inhibitor (meclofenamate), NO synthase (NOS) inhibitor (NG-monomethyl-l-arginine, l-NMMA), NO clamp (l-NMMA + sodium nitroprusside), or placebo. Effectiveness of COX inhibition was tested by measuring urinary prostaglandin E2 (UPGE2). Effectiveness of NOS blockade and NO clamp was determined by urinary NO degradation products (UNOx). Exenatide increased GFR, UV, UPGE2, and UNOx. Pretreatment with meclofenamate reduced UPGE2 by 75% and reduced the effect of exenatide on UPGE2 by 30% but did not modify the effects of exenatide on GFR or UV. Pretreatment with l-NMMA reduced UNOx and the impact of exenatide on GFR and UV by 50%. Pretreatment by NO clamp did not prevent UNOx from increasing during exenatide but blunted the effects of exenatide on GFR and UV. In conclusion, exenatide is a potent renal vasodilator and diuretic in the rat. These effects of exenatide are insensitive to COX inhibition but are mediated, in part, by NO.