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.

Biochemical study of prolactin binding sites in Xenopus laevis brain and choroid plexus.

The occurrence of prolactin binding sites in some brain structures (telencephalon, ventral hypothalamus, myelencephalon, hypophysis, and choroid plexus) from Xenopus laevis (anuran amphibian) was studied by the in vitro biochemical technique. The higher binding values were obtained at the level of the choroid plexus and above all of the hypothalamus. On the bases of hormonal specificity and high affinity, these binding sites are very similar to those of prolactin receptors of classical target tissues as well as of those described by us in other structures from Xenopus.

Further study on the changes in the concentration of prolactin-binding sites in different organs of Xenopus laevis male and female, kept under dry conditions and then returned to water (their natural habitat).

The binding of 125I-labeled ovine prolactin (125I-oPRL) to membranes from the kidney and liver of Xenopus laevis male and female specimens (Experiment I) and from the kidney, epidermis, and liver of female specimens (Experiment II) (1) kept in an aquatic environment, (2) exposed for 2 weeks to dehydrating conditions, and (3) then placed back into their aquaria after exposure to dehydrating conditions (Experiment II) was studied. No significant sex differences in PRL binding to kidney, epidermis, and liver were found. A highly significant drop in PRL specific binding to the membranes from the kidney and epidermis is brought about in the specimens from both sexes exposed to dehydrating conditions.

Prolactin binding sites in Xenopus laevis tissues: comparison between normal and dehydrated animals.

The binding of 125I-labeled ovine prolactin (125I-oPRL) to membranes from the kidney, epidermis, liver, and testis of Xenopus laevis adult specimens either kept in an aquatic environment or exposed for 2 weeks to dehydrating conditions was studied. Prolactin binding specificity was assayed through competition with several unlabeled hormones (oPRL, hGH, rGH, rLH, and porcine insulin). In the animal exposed to dehydrating conditions a statistically highly significant reduction in prolactin binding to the membranes from the kidney and epidermis was recorded.