Effects of gonadal hormones on calcium-binding protein in chick duodenum

¹ Departments of Genetics and Development, and Physiology and Biophysics, University of Illinois, and School of Basic Medical Sciences, University of Illinois College of Medicine, Urbana, Illinois 61801

The effect of the sex steroid hormones (estrogen, progesterone, and testosterone) and vitamin D₃, alone or in various combinations, on duodenal calcium-binding protein (CaBP) and wet weight was investigated in 7.5- to 10-wk-old female chicks. Chicks were either vitamin D-deficient or vitamin D-replete. Hormones were injected for 1, 2, 3, 4, or 8 days. The design in which injections were made for 8 days proved best for testing the effects of the gonadal hormones. Whereas neither diethylstilbestrol (DES, a synthetic estrogen), progesterone, nor testosterone, alone or in combination, could directly increase CaBP, DES did enhance the vitamin D-stimulated increase in CaBP in rachitic chicks. DES also significantly increased the CaBP levels in vitamin D-replete chicks, working, presumably, through endogenous vitamin D₃. Moreover, in 8-day treatments, DES increased duodenal weight. In contrast, testosterone did not augment the action of vitamin D in either vitamin D-replete or -deficient chicks. Although progesterone did not enhance the action of vitamin D in rachitic chicks, when administered for 8 days to vitamin D-replete chicks, it significantly increased CaBP levels, although to a much smaller extent than did DES. In vitamin D-replete chicks, concomitant administration of progesterone or testosterone inhibited the DES-induced increase in CaBP levels. Hence the gonadal hormones appear capable of modulating the action of vitamin D in the regulation of CaBP concentration in the duodenum.

Submitted on September 21, 1978
Accepted on May 23, 1979