CALBINDIN-D28K DISTRIBUTION IN CHICK ULTIMOBRANCHIAL AND RAT THYROID GLANDS

Publisher Summary This chapter describes the calbindin-D 28k distribution in chick ultimobrancial and rat thyroid glands. Calbindin-D 28k [CaBP], the vitamin D-dependent calcium binding protein, appears as an end-organ marker of the vitamin D endocrine system in several tissues. The protein was first discovered in chick intestine and subsequently in other chick tissues. CaBP is also present in other species and a lower molecular weight form, calbindin-D9K, predominates in mammalian intestine. White Leghorn cockerels were raised on a normal diet and sacrificed from 4 days to 5 weeks of age. Mature Sprague-Dawley rats, raised on a normal diet, were also utilized. The UB glands from chicks and thyroids from rats were rapidly dissected, quick-frozen and fixed by freeze substitution. After fixation, embedding in paraffin, sectioning and deceration, the sections were reacted immunohistochemically with anti-CaBP. The connective tissue elements of the UB gland and the isolated islands of parathyroid tissue did not contain CaBP. It is found that when UB gland sections adjacent to those stained for CaBP were reacted with anti-CT, the co-localization of CaBP and CT was observed.