Thesis (M.Sc.)--Chulalongkorn University, 1995

The aim of the present study was to study the effects of L-arginine which relating to nitric oxide synthesis on the renal function and general circulation in dogs. Whether these changes are mediated by renin-angiotensin or prostaglandin system during L-arginine loading following with administration of L-Name ; inhibitor of the nitric oxide synthesis (Group I) or following with administration of the combination of L-Name and enalapril maleate (Group II) or following with administration of the combination of L-Name and indomethacin (Group III). The animals given L-arginine following with L-Name alone, showed significantly decreased in heart rate (P<0.05) while mean arterial blood pressure was significantly increased (P<0.001) (Group I). In group I, a marked decrease in both renal plasma flow and renal blood flow (P<0.05) coincided with increase in renal vascular resistance (P<0.01) and total peripheral resistance was observed after L-Name administration. By administration of the combination of L-Name and indomethacin after L-arginine loading (Group III), the pattern of changes of general circulation and renal hemodynamics were similar way as those occured in group I. Total peripheral resistance was significantly increase (P<0.001) in this group. In both group I and group II, urine flow rate were slightly decreasee whereas urinary excretion of sodium was slightly increasee. Administration of the combination of L-Name and enalapril maleate after L-arginine loading (Group II), the decrease in heart rate (P<0.01), mean arterial blood pressure coincided with slightly increase in total peripheral resistance were noted. Renal plasma flow and renal blood flow were decreased in compariosn with L-arginine infusion period. Urinary excretion of sodium was slightly decreased. In all groups, plasma concentation of sodium did not alter throughout the experimental period. In group I and II, plasma concentations of potassium and chloride in the fourth period were increased (P<0.01) but plasma concentation of chloride did not alter in group III. These data may indicate that nitric oxide, which is synthesized from L-arginine, can be inhibited by L-Name administration. The actions of nitric oxide on both renal hemodynamics and general circulation might possible relate to renin-angiotensin system but was not related to prostaglandin system