NUCLEAR RECEPTORS FOR 1,25-DIHYDROXY-22-OXAVITAMIN D-3 (OCT) AND 1,25-DIHYDROXYVITAMIN D-3 IN GASTRIC GLAND NECK MUCOUS CELLS AND GASTRIN ENTEROENDOCRINE CELLS

22-Oxacalcitriol the analog with low calcemic effect and the original hormone 1,25(OH)(2) vitamin D-3 were localized by autoradiography in m ouse stomach at different time intervals after intravenous injection, Both compounds showed a distinct nuclear concentration and retention i n neck mucous cells of gastric and pyloric glands, and in dispersed en docrine cells in the antrum region. When the nuclear binding of radioa ctively labelled compound was compared between gastric neck cells and duodenal absorptive cells, binding was low but sustained in neck cells . Peak uptake after the injection was between 8 and 12 h in neck cells , but between 15 min and 30 min in duodenal villous epithelium. In the duodenum, weak nuclear labelling appeared at 8 h and was undetectable at 12 h under the conditions of the experiment. Nuclear labelling of neck cells remained detectable at 12 h and even after 24 h, similarly for both OCT and 1,25(OH)(2) vitamin D-3. These results suggest that t he stomach is an important target tissue for vitamin D and its analog OCT. Regulation of neck cell functions is suggested, such as prolifera tion and differentiation of surface epithelium and gastric gland epith elium, and neck cell secretion of acidic mucus. Regulation is also ind icated of G-cell gastrin secretion associated with gastrin paracrine e ffects on parietal cell HCl and intrinsic factor secretion, chief cell pepsinogen secretion, neck cell proliferation, as well as endocrine e ffects on systemic calcium homeostasis.