Human growth hormone increases intestinal vitamin D-dependent calcium-binding protein in hypophysectomized rats.
We examined the effects of hypophysectomy and pituitary hormone replacement on vitamin D-dependent calcium-binding protein (CaBP) in rat small intestine. The concentration of immunoreactive CaBP per mg intestinal protein was decreased by at least 56% in hypophysectomized rats compared to that in intact pair-fed controls. Alkaline phosphatase and total protein also were reduced by hypophysectomy, but pair-feeding produced comparable decreases. Daily injections of 2, 10, or 50 micrograms human GH (hGH) for 9 days produced a dose-dependent increase in CaBP. At the highest hGH dose (50 micrograms), the content of CaBP was increased 2- to 4-fold to intact levels. By comparison, the increases in total protein and alkaline phosphatase were small (25% to 40% and 80% to 90%, respectively). The induction of CaBP preceded the other protein responses; half-maximal increases in CaBP occurred after 2 days of hGH (50 micrograms/day) treatment before statistically significant changes in total protein or alkaline phosphatase activity. hGH was the most potent pituitary hormone tested; ovine TSH (25 mU/day) had no effect on CaBP, and ovine PRL (10 or 50 micrograms/day) increased CaBP by only 25-27% (P = 0.014). These studies indicate that the vitamin D-dependent intestinal CaBP in hypophysectomized rats is regulated by GH and provide further evidence that the pituitary may be involved in regulating vitamin D-dependent intestinal adaptations.
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D004435:Eating / Q000187:drug effects; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology*; D007016:Hypophysectomy; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D011388:Prolactin / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D051381:Rats; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology
D002135:Calcium-Binding Proteins; D011506:Proteins; D064030:S100 Calcium Binding Protein G; D011388:Prolactin; D013972:Thyrotropin; D013006:Growth Hormone; D000469:Alkaline Phosphatase