The proposed research represents a continuation of the investigation on the transport of calcium and other mineral ions across the intestine. Emphasis will be given to vitamin D and other factors that control mineral ion absorption and intestinal function. Specific studies to be undertaken within this grant period are, as follows: a) Continued investigation of the function vitamin D and calbindin-D28K in Ca2+ transport across epithelial membranes and continued investigation of the ATP-dependent calcium pump, with emphasis on the responsiveness of the pump to vitamin D and calbindin-D28K; b) Investigate the state and localization of calcium and other mineral ions during the course of transepithelial transport using spectrofluorometry with fluorescent calcium indicator dyes (fura 2; quin 2) for free Ca2+, and ion microscopy for total Ca2+. Chlortetracycle, another fluorescent Ca2+ indicator, will be examined as a probe for intravesicular Ca2+; c) Investigate the mechanism or mechanisms of magnesium transport across the intestine and other epithelial tissues, and the role of vitamin D and other affectors on its transport and metabolism; d) Investigate the effect of vitamin D on the function of the intestinalis nerve of the chick, the latter shown to contain vitamin D-responsive calbindin-D28K, using various neurophysiological and biochemical approaches. e) Continued studies on the effect of E. coli heat stable enterotoxin and cGMP on the Ca2+ permeability of the enterocyte, and f) Continued studies on the mechanism of selenite absorption and the relation of vitamin D-dependent selenite absorption and the relation of vitamin D-dependent selenite transport to other anion transport systems.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Method to Extend Research in Time (MERIT) Award (R37)
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Cornell University
Schools of Veterinary Medicine
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