Circannual changes in plasma aldosterone levels in Bufo japonicus formosus

Plasma aldosterone levels of Bufo japonicus formosus captured in their natural environment were determined each month throughout 1 year by radioimmunoassay. Low values were recorded in winter and spring, and the maximum occurred in July or August. High summer levels of aldosterone and increases in live weight were correlated. This phenomenon could reflect the gluconeogenetic action of aldosterone. In females but not in males, relatively high levels of plasma aldosterone were also observed in autumn; the relatively high levels of estrogen during this season may stimulate interrenal activity. This could be important to provide additional energy for ovogenesis which occurs in the autumn. On the other hand, high levels of androgen in males may reduce interrenal activity. Aldosterone seems to play no direct role in emergence from water after aquatic breeding activity in spring, as plasma levels showed no significant change during this season.