Prolactin increases lipid fluidity and prolactin binding of rat prostatic membranes

The objective of these studies was to determine whether prolactin could modify the lipid fluidity of rat ventral and dorsolateral prostate membranes and subsequently modify the availability of prolactin receptors. Additional studies were also undertaken to determine the effects of prolactin on serum lipid fluidity. Adult male rats were injected with 0, 100, or 400 micrograms ovine prolactin/day subcutaneously for a period of 5 days. Serum and prostatic membrane lipid fluidity was measured by a fluorescence polarization method using a lipid probe 1,6-diphenylhexatriene. Prolactin binding in dextran-coated charcoal-pretreated prostatic membranes was determined by radioreceptor assay. This pretreatment has been reported by us to remove the endogenous substances that interfere with prolactin binding assay (J. R. Dave and R. J. Witorsch, Endocrinology 111: 2144-2146, 1982). Prolactin binding increased by approximately 44 and 72% in dorsolateral prostate and 16 and 39% in ventral prostate in 100- and 400-micrograms groups, respectively. Membrane fluidity increased by approximately 16 and 19% in dorsolateral prostate and 10 and 13% in ventral prostate in 100- and 400-micrograms groups, respectively. Serum lipid fluidity increased 50 and 79% in 100- and 400-micrograms groups, respectively.