[The effect of angiotensin I converting enzyme inhibitor (SQ 14225) on plasma 18-hydroxycorticosterone and aldosterone in sodium depleted conscious rats].

Altered sodium intake is known to cause a greater change in plasma 18-hydroxycorticosterone (18-OHB) level than in plasma aldosterone level, resulting in an increase of plasma 18-OHB/aldosterone ratio in sodium-depleted man and rats. To evaluate the role of endogenous angiotensin II in the high plasma 18-OHB/aldosterone ratio in sodium-depleted rats, we examined the effect of the angiotensin I converting enzyme inhibitor SQ 14225 on plasma 18-OHB and aldosterone in sodium-depleted (SD) and sodium-repleted (SR) conscious rats. Plasma renin activity (PRA) and plasma angiotensin II were higher in the SD rats than in the SR rats. The ingestion of SQ 14225 caused an increase in PRA and a decrease in plasma angiotensin II, whereas these changes were more prominent in the SD rats than in the SR rats. Plasma 18-OHB and aldosterone levels were higher in the SD rats than in the SR rats. The plasma 18-OHB/aldosterone ratio was also higher in the SD rats than in the SR rats. The ingestion of SQ 14225 caused decreases in plasma 18-OHB and aldosterone levels in both the SR and SD rats, whereas the SQ 14225-induced decreases in plasma 18-OHB and aldosterone levels were more prominent in the SD rats than in the SR rats. Thus, the ingestion of SQ 14225 induced a decrease in the plasma 18-OHB/aldosterone ratio in both the SR and SD rats. The decrease in plasma 18-OHB/aldosterone ratio was more prominent in the SD rats than in the SR rats.(ABSTRACT TRUNCATED AT 250 WORDS)