Effects of the Sex Steroid Hormones and Vitamin D3 on Calcium-Binding Proteins in the Chick Shell Gland1

The effects of diethylstilbestrol (DES), progesterone, testosterone and vitamin D3, alone or in various combinations, on the calcium-binding protein (CaBP) concentration, wet weight and histology of the shell gland were investigated in 7.5–10-week-old chicks. Chicks, which were either vitamin D deficient or vitamin D replete, were pretreated with DES to differentiate the shell gland. DES administration was then discontinued for 10 days and then chicks were treated with the hormones to be tested. In this secondary treatment period, DES increased the levels of CaBP (measured using a specific radioimmunodiffusion assay) in both vitamin D deficient and vitamin D replete chicks, suggesting an effect of DES on CaBP largely independent of vitamin D. Progesterone alone had no effect on CaBP levels, but it inhibited the DES stimulated increase in CaBP in every case tested. In contrast to this antagonism of CaBP level, the increases in shell gland wet weight and hypertrophy of the tubular gland cells induced by DES were not inhibited by concomitant progesterone administration. Vitamin D3 alone did not increase CaBP concentration in the shell gland and, when administered with DES to vitamin D deficient chicks, it elicited little if any increase in CaBP level above that evoked by DES alone. Testosterone had little effect on CaBP level in the shell gland. Despite chronic injections with estrogen, however, the maximum concentration of CaBP induced in the DES-differentiated shell gland was only one-sixth the concentration found in the shell gland of the egg laying hen. These results indicate that CaBP, which is found in numerous organs, may be regulated by factors in addition to vitamin D3, the predominant regulator in the intestine, and that estrogen and progesterone may play important roles in modulation of CaBP concentration in the shell gland of the hen.