Role of ouabain-like compound in the regulation of plasma aldosterone concentration in rats

A major biologically active Na,K-ATPase inhibitor in the mammalian circulation may be ouabain-like compound(OLC). We developed a population of immunized rats against ouabain to block the actions of circulating OLC. To investigate the roles of OLC in the regulation of aldosterone secretion and/or production, we measured plasma aldosterone concentration after a week of low salt diet. No significant changes in serum Na and K concentrations were observed in immune rats. The plasma aldosterone concentration was significantly decreased by 30% in 17 immune rats as compared with 11 control rats(control: 455 +/- 53, immune: 315 +/- 21 pg/mL, p < 0.05). These data indicate that chronic blockade of the circulating OLC significantly decreases plasma aldosterone concentration during salt depletion and suggest that endogenous OLC may play an important role in the regulation of aldosterone secretion and/or production.