title: Tissue-specific regulation of shell gland calbindin D28K biosynthesis by estradiol in precociously matured, vitamin D-depleted chicks.
abstract: 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.
authors.affiliation: Department of Physiology, New York State College of Veterinary Medicine, Cornell University, Ithaca 14853.
authors.forename: R A
authors.initials: RA
authors.lastname: Corradino
authors.forename: C A
authors.initials: CA
authors.lastname: Smith
authors.forename: L P
authors.initials: LP
authors.lastname: Krook
authors.forename: C S
authors.initials: CS
authors.lastname: Fullmer
mesh_terms: D000818:Animals; D064026:Calbindins; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002645:Chickens; D004032:Diet; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism; D004528:Egg Shell; D004958:Estradiol / Q000494:pharmacology*; D005088:Exocrine Glands / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006706:Homeostasis; D007150:Immunohistochemistry; D007408:Intestinal Absorption / Q000187:drug effects; D010057:Oviducts / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000096:biosynthesis*; D014808:Vitamin D Deficiency / Q000378:metabolism*
chemical_list: D064026:Calbindins; D064030:S100 Calcium Binding Protein G; D004958:Estradiol; D000252:Calcium-Transporting ATPases; D002118:Calcium