REGULATION OF PROLACTIN RECEPTOR MESSENGER-RNA EXPRESSION IN PERIPHERAL LYMPHOCYTES IN RATS IN RESPONSE TO CHANGES IN SERUM CONCENTRATIONS OF PROLACTIN

In the present study we have evaluated the absolute number of the two forms of prolactin (PRL) receptor mRNA in rat peripheral blood lymphoc ytes and the modulation of receptor mRNA induced by changes in serum l evels of endogenous PRL or by administration of ovine PRL. Lymphocytes expressed low levels of both forms of PRL, receptor transcripts. Repe ated treatments with ovine PRL significantly reduced levels of mRNA en coding the long form PRL receptor, whereas expression was markedly inc reased by repeated doses of bromocriptine. In contrast, the mRNA level of short form PRL receptor was unchanged by both treatments. The expr ession of long form transcripts was also markedly decreased in lymphoc ytes from pituitary-grafted rats. Therefore it appears that in rat per ipheral lymphocytes PRL has epsilon negative effect on the expression of its own receptor.