Immunocytochemical localization of prolactin receptors in rat liver cells: I. Dependence on sex and sex steroids.

The peculiarities of cellular and tissue distribution of prolactin receptors (PRLR) in the liver of female and male rats with different sex steroid status were investigated in paraplast-embedded tissue with the indirect immunoperoxidase technique. Two clones of antibodies directed outside the PRL-binding site (U6) or to the PRL-binding site (T6) of the receptor were used. PRLR-specific immunoreactivity was identified essentially in hepatocytes. PRLR can be visualized in sinusoidal domains of cellular membranes, in cytoplasmic granules and sometimes in the perinuclear area of hepatocytes. The staining characteristics were similar with both antibodies. There were no prominent differences in the intensity of PRLR-positive staining among hepatocytes of different zones of hepatic lobules with the exception of some hepatocytes around central veins. Sex differences in the intensity of immunostaining (strong in females, and faint in males) but not in the amount and distribution of PRLR-containing cells were observed. Gonadectomy of animals caused the disappearance of sex differences in the intensity of PRLR-positive staining as a result of its decrease in females and increase in males. The essential elevation in the intensity of PRLR-specific immunoreactivity was revealed in hepatocytes of gonadectomized females and males after prolonged estradiol administration (10 micrograms for 14 days). The cytoplasmic staining of some hepatocytes surrounding central veins was much more pronounced in estrogenized animals. PRLR-specific immunoreactivity in the perinuclear area was identified in these cells. Androgen treatment (3 mg of testosterone-propionate for 3 days) of gonadectomized animals caused a decrease in the intensity of hepatocyte PRLR-positive staining similarly in both sexes.(ABSTRACT TRUNCATED AT 250 WORDS)