Induction of prolactin receptors in rat liver after the administration of growth hormone.

Abstract

The pituitary regulation of the sexually differentiated PRL receptor in rat liver was studied. PRL receptors were measured in a crude membrane fraction (105,000 × g pellet) using [125I]iodohuman PRL as tracer. Human GH (hGH), continuously administered by Alzet osmotic minipumps with an infusion rate of 5 μg/h for 1 week, was shown to induce PRL receptors in livers from male and female hypophysectomized-gonadectomized rats. The PRL receptors were increased to a level found in control female rat livers. This inductive effect of hGH was also seen in adrenalectomized and thyroidectomized male rats. In intact male rats given hGH, PRL receptors were increased to a female level in 4–7 days. hGH was effective in doses of 2.5 and 5 Μg/μl in inducing a female receptor pattern. The induced PRL receptors in male rats had characteristics similar to those of hepatic PRL receptors in female rats when data were calculated according to Scatchard (Kd = 0.13 × 10-9 vs. 0.15 × 10-9 M; number of binding sites 88 vs. 57 fmol/m...