Different Effects of 7-nitroindazole and L-NAME Administered Both Individually and Together on the Cardiovascular System of the Rat

We evaluated the effects of N(G)-nitro-L-arginine methylester (L-NAME) (50 mg/kg/day) and 7-nitroindazole (7NI) (10 mg/kg/day) administered from 10th-16th week of age either individually or together on cardiovascular system of Wistar rats and SHR. Systolic blood pressure (sBP) was measured weekly by the plethysmographic method. For morphological studies, the animals (n=10) were perfused with a fixative (120 mm Hg), and thoracic aorta and carotid and coronary arteries were processed for electron microscopy. For functional investigation (n=10), aortic rings were used in an organ bath. In Wistar rats, L-NAME evoked an increase of sBP; hypertrophy of the heart and arterial walls; an increase in cross-sectional areas (CSA) of endothelial cells (EC), muscle cells (SMC), extracellular matrix (ECM), and a decrease in acetylcholine-induced endothelial-dependent relaxation (EDR). 7NI evoked sBP-independent hypotrophy of the heart and arterial walls, a decrease in CSA of EC and SMC without affecting the CSA of ECM, and a mild decrease in acetylcholine-induced EDR. 7NI and L-NAME administered together evoked lower effect on BP and trophicity of the heart and all arteries, and a similar decrease in acetylcholine-induced EDR compared to L-NAME alone. In SHR, 7NI did not evoke any effect on the studied parameters.