The mechanism underlying this phenomenon is largely unknown. This study was designed to investigate the involvement of endothelin (ET)-1 and nitric oxide (NO) systems in IAP-induced renal dysfunction. Rats were subjected to IAP of 14 mmHg for 1 h, followed by a deflation for 60 min (recovery). Four additional groups were pretreated with 1) ABT-627, an ET A antagonist; 2) A-192621, an ETB antagonist; 3) nitroglycerine; and 4) N G -nitro-L-arginine methyl ester, a NO synthase inhibitor, before IAP. Urine flow rate (V), absolute Na ϩ excretion (UNaV), glomerular filtration rate (GFR), and renal plasma flow (RPF) were determined. Significant reductions in kidney function and hemodynamics were observed when IAP was applied. V decreased from 8.1 Ϯ 1.0 to 5.8 Ϯ 0.5 l/min, UNaV from 1.08 Ϯ 0.31 to 0.43 Ϯ 0.10 eq/min, GFR from 1.84 Ϯ 0.12 to 1.05 Ϯ 0.06 ml/min (Ϫ46.9 Ϯ 2.7% from baseline), and RPF from 8.62 Ϯ 0.87 to 3.82 Ϯ 0.16 ml/min (Ϫ54 Ϯ 3.5% from baseline). When the animals were pretreated with either ABT-627 or A-192621, given alone or combined, the adverse effects of IAP on GFR, RPF, V, and UNaV were significantly augmented. When the animals were pretreated with nitroglycerine, the adverse effects of pneumoperitoneum on GFR and RPF were substantially improved. In contrast, pretreatment with N G -nitro-L-arginine methyl ester remarkably aggravated pneumoperitoneum-induced renal dysfunction. In conclusion, decreased renal excretory function and hypofiltration are induced by increased IAP. These effects are related to impairment of renal hemodynamics and could be partially ameliorated by pretreatment with nitroglycerine and aggravated by NO and ET blockade.rat; intra-abdominal pressure PNEUMOPERITONEUM AT PRESSURE above 10 mmHg during laparoscopic surgery has been shown to produce transient oliguria and reduced glomerular filtration rate (GFR) and renal blood flow (RBF) (3,9,16,33,34). Despite much research in this field, the systemic physiological consequences of CO 2 pneumoperitoneum and the mechanisms underlying its adverse effects on renal hemodynamics and excretory function are not fully understood (9). However, there is compelling experimental evidence that the adverse renal effects induced by pneumoperitoneum are affected by the level of intra-abdominal pressure (IAP), volume status, degree of hypercarbia, positioning, and individual hemodynamic and renal reserves (9, 10). Additional factors that may affect renal function during pneumoperitoneum include direct compression of the renal parenchyma and renal vein (4, 17), increased resistance in the renal vasculature (47), and release of vasoconstrictors, such as vasopressin, angiotensin II, catecholamines, and endothelin (ET)-1 (1, 13). The latter is a very potent natural mammalian vasoconstrictor agent (25), acting on the cardiovascular and renal systems and other target organs by binding to two major types of receptors, ET A and ET B (2,25,36). High abundance of ET A receptors has been detected in the aorta, heart, and kidney, whereas ET B receptors are expre...