Endocrinology, Vol 132, 193-198, Copyright © 1993 by Endocrine Society

ARTICLES

Tissue-specific regulation of shell gland calbindin D28K biosynthesis by estradiol in precociously matured, vitamin D-depleted chicks

RA Corradino, CA Smith, LP Krook and CS Fullmer
Department of Physiology, New York State College of Veterinary Medicine, Cornell University, Ithaca 14853.

Provision of Ca2+ for egg shell calcification in the avian uterus [egg shell gland (ESG)] derives mostly from vitamin D-dependent intestinal Ca2+ absorption from the diet. Ca2+ absorption is strongly linked to the intestinal vitamin D-dependent calbindin D28K (D28K) concentration. The laying hen ESG also contains D28K, and again, Ca2+ transport into the shell appeared to be linked to the ESG D28K concentration. However, evidence is now presented that ESG D28K synthesis may be estradiol (E2) dependent and vitamin D independent under certain conditions. One-day- old female chicks fed a vitamin D-free diet for as long as 6 weeks and then repeatedly injected im with E2 for up to 3 more weeks developed frank rickets, but possessed precociously matured reproductive tracts. While the tiny presumptive ESGs of nonestrogenized vitamin D-depleted chicks were devoid of D28K, the highly developed ESG, including the isthmus, of estrogenized chicks contained D28K. The ESGs of nonestrogenized, vitamin D-replete chicks also exhibited no development or detectable D28K. Regardless of whether vitamin D depleted or replete, estrogenized chick ESG contained similar D28K and D28K mRNA concentrations. Immunohistochemical techniques showed that the endometrial cellular localization of both D28K and Ca(2+)-ATPase (Ca2+ pump) in estrogenized chicks was similar to that in mature laying hens. There was no trace of D28K, nor was there any stimulation of Ca2+ absorption, in duodenum of vitamin D-free, immature chicks regardless of E2 treatment. As expected, both D28K and D28K mRNA were present in vitamin D-replete chick duodenum. We conclude that in E2-treated chicks, ESG D28K gene expression may be vitamin D independent and E2 dependent. This is the first clear demonstration of hormone-dependent tissue-specific D28K gene expression in the chick.

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				I. Lavelin, N. Meiri, O. Genina, R. Alexiev, and M. Pines Na+-K+-ATPase gene expression in the avian eggshell gland: distinct regulation in different cell types Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2001; 281(4): R1169 - R1176. [Abstract] [Full Text] [PDF]