An in vitro stimulatory effect of indoleamines on aldosterone biosynthesis in the rat

The effect of the indoleamines, serotonin, 5-methoxy-tryptamine, 5-methoxytryptophol and melatonin on aldosterone biosynthesis by rat adrenals in vitro has been studied. In all experiments incremental doses of each of the indoleamines tested produced a progressive increase in aldosterone secretion. Serotonin (10(-6) mol/l) produced a 5-fold increase in aldosterone secretion by isolated perfused rat zona glomerulosa cells obtained from animals on a normal sodium diet compared to the basal levels. Higher (9-fold) responses were elicited when the cells were from sodium deficient rats and lower (3-fold) when the rats were sodium loaded. 5-methoxytryptamine (10(-6) mol/l) was a more potent aldosterone agonist (8-fold increase) and the aldosterone response was similarly affected by change in sodium intake. Smaller responses were found when cells were stimulated by 5-methoxytryptophol (10(-4) mol/l, 3.5-fold) or melatonin (10(-4) mol/l, 3-fold). The dopamine agonist serotonin antagonist Lisuride completely inhibited the aldosterone response to 5-methoxytryptamine (10(-8) mol/l) and serotonin (10(-7) mol/l). These results suggest that pineal indoles could play a role in aldosterone biosynthesis and indicate that changes in sodium balance affect the aldosterone response to indoles in the same way as has been described for other aldosterone secretagogues.