ALTERED REGULATION OF SERUM PROLACTIN IN NUDE-MICE

Congenitally athymic (nude) mice have severe deficiencies in reproduct ive function, with reduced circulating levels of gonadotrophins and go nadal steroids. Since little is known about the impact of athymia on p rolactin (Prl) cell morphology and regulation, we undertook to assess prolactotrophic cell morphology and Prl serum levels in nude mice unde r basal and stressful conditions, taking as a reference their euthymic normal counterparts. Normal and nude CD-I mice were subjected to l-h immobilisation stress and then allowed to recover for 60 min. Serum le vels of Prl were assessed by RIA at 0, 30 and 60 min post-stress. Athy mic animals showed significantly lower basal levels of serum Prl than their normal counterparts but immunohistochemical assessment of the pr olactotrophic cell population revealed a normal morphology in the athy mic animals. A definite (0.05 < p < 0.07) increase in Prl levels in no rmal and, to a lesser extent, nude animals was observed immediately af ter stress termination. This effect was followed by a marked reduction in circulating Prl which reached below-basal concentrations at 30 and 60 min post-stress. We conclude that the hypoprolactinaemic condition of the nude mouse is not due to primary hypopituitarism but to a defi cient control or responsiveness of their pituitary gland.