Role of the renin-angiotensin system in drinking of seawater-adapted eels Anguilla japonica: a reevaluation

Role of the renin-angiotensin system in drinking of seawater-adapted eels Anguilla japonica: a reevaluation. Am J Physiol Regulatory Integrative Comp Physiol 279: R1105-R1111, 2000.--The role of ANG II, a potent dipsogenic hormone, in copious drinking of seawater eels was examined. SQ-14225 (SQ), an angiotensin-converting enzyme inhibitor, infused intra-arterially at 0.01-1 [micro]g [multiplied by] [kg.sup.-1] [multiplied by] [min.sup.-1], depressed drinking and arterial blood pressure in a dose-dependent manner. The inhibition was accompanied by a small decrease in plasma ANG II concentration, which became significant at 1 [micro]g [multiplied by] [kg.sup.-1] [multiplied by] [min.sup.-1]. After the infusate was changed back to the vehicle, the depression of drinking and arterial pressure continued for [is greater than] 2 h, although plasma ANG II concentration rebounded above the level before SQ infusion. By contrast, infusion of anti-ANG II serum (0.01-1 [micro]g [multiplied by] [kg.sup.-l] [multiplied by] [min.sup.-1]) did not suppress drinking and arterial pressure, although plasma ANG II concentration decreased to undetectable levels. Plasma atrial natriuretic peptide and plasma osmolality. which influence drinking rate in eels, did not change during; SQ or antiserum infusions. These results suggest that the renin-angiotensin system plays only a minor role in the, vigorous drinking observed in seawater eels. The results also suggest that the antidipsogenic and vasodepressor effects of SQ in seawater eels are not due solely to the inhibition of ANG II formation in plasma. converting enzyme inhibition by SQ-14225; immunoneutralization of angiotensin II; water intake; blood pressure; atrial natriuretic peptide