부산대학교 도서관

The responses to infusion of nitric oxide synthase substrate (L-arginine 3 mg*[kg.sup.-1]*[min.sup.-1]) and to slow volume expansion (saline 35 ml/kg for 90 rain) alone and in combination were investigated in separate experiments. L-Arginine left blood pressure and plasma ANG II unaffected but decreased heart rate (6 [+ or -] 2 beats/min), and urine osmolality, increased glomerular filtration rate (GFR) transiently, and caused sustained increases in sodium excretion (fourfold) and urine flow (0.2 [+ or -] 0.0 to 0.7 [+ or -] 0.1 ml/min). Volume expansion increased arterial blood pressure (102 [+ or -] 3 to 114 [+ or -] 3 mmHg), elevated GFR persistently by 24%, and enhanced sodium excretion to a peak of 251 [+ or -] 31 [micro]mol/min, together with marked increases in urine flow, osmolar and free water clearances, whereas plasma ANG II decreased (8.1 [+ or -] 1.7 to 1.6 [+ or -] 0.3 pg/ml). Combined volume expansion and L-arginine infusion tended to increase arterial blood pressure and increased GFR by 31%, whereas peak sodium excretion was enhanced to 335 [+ or -] 23 [micro]mol/min at plasma ANG II levels of 3.0 [+ or -] 1.1 pg/ml; urine flow and osmolar clearance were increased at constant free water clearance. In conclusion, L-arginine 1) increases sodium excretion, 2) decreases basal urine osmolality, 3) exaggerates the natriuretic response to volume expansion by an average of 50% without persistent changes in GFR, and 4) abolishes the increase in free water clearance normally occurring during volume expansion. Thus L-arginine is a natriuretic substance compatible with a role of nitric oxide in sodium homeostasis, possibly by offsetting/shifting the renal response to sodium excess. sodium excretion; free water clearance; angiotensin