Effects of Aminoglutethimide on Levels of Messenger Ribonucleic Acid of CaBP-D28K and of Vitamin D3 Receptor in the Shell Gland of Laying Hen.

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This study was conducted to evaluate the role of sex steroids on the gene expression of vitamin D dependent calcium binding protein, calbindin-D28K (CaBP-D28K), and vitamin D3 receptor (VDR) in the laying hen. Aminoglutethimide (AGT), an inhibitor of steroidogenesis, was administered to laying hens 5 hours after ovulation to block ovarian steroidogenesis. The CaBP-D28K and VDR mRNA levels in the intestine and shell gland were determined 4 hours after AGT administration. Plasma Ca levels and egg shell weight were also measured. AGT significantly suppressed both CaBP-D28K and VDR mRNA levels in the intestine and shell gland. In the shell gland, the levels of CaBP-D28K and VDR mRNAs decreased in the AGT treatment group and supplements of progester-one (P4) or estradiol benzoate (EB) did not restore either mRNA levels. Although plasma Ca concentration decreased slightly after AGT injection, the administration of EB restored Ca levels to control values. In the intestine, the effects of AGT and steroid supplements were similar to those in the shell gland. This report clearly shows that sex steroids influence the expression of CaBP-D28K and VDR genes and Ca2+ flux in the intestine and shell gland during egg shell calcification. However, the expression of the CaBP-D28K and VDR genes and Ca2+ flux are not regulated by a single steroid such as progesterone or estrogen in laying hen.
日本家禽学会の論文