Prolactin and interrenal hormone balance in adult specimens of Xenopus laevis exposed to hyperosmotic stress for up to one week.

Adult female specimens of Xenopus laevis were exposed to diluted artificial seawater for up to 1 week. Statistically significant increases were observed in serum levels of aldosterone and corticosterone, concomitant with a drop in levels of prolactin (PRL) receptors in the cell membranes of the epidermis and kidney, which can be taken as an indicator of the levels of circulating PRL. The changes in hormone levels were detected after 1 day, being followed by a gradual restoration of the initial mean levels of these hormones when the exposure to hyperosmotic stress was extended for up to 2 or 7 days. Comparison of the above results with those previously obtained in Xenopus after longer exposure (15 days) to brackish water substantiates the necessity of recording possible initial fluctuations, as well as any changes that occur over the course of longer exposure during which time adaptation to environmental changes are likely to take place. The reverse responses, which may be not independent of one another, in terms of levels of corticoids and PRL in the animals exposed to hyperosmotic stress, are discussed. A survey of the literature suggests that, in Xenopus, as in the case of other less strictly water-dwelling amphibians, PRL is one of the hormones required for life in fresh water.