Nongenomic effects of 1,25-dihydroxyvitamin D3: potential relation of a plasmalemmal receptor to the acute enhancement of intestinal calcium transport in chick.

A number of model systems now exist for studying the nonnuclear actions of the seco-steroid hormone 1,25(OH)2D3. The perfused duodenal loop of vitamin D-replete chicks has provided the best correlation between nonnuclear actions and a physiological end point, namely enhanced calcium transport. Recent progress has been made in identifying and purifying an integral protein of the basal lateral membrane that may be a receptor for 1,25(OH)2D3. Studies with analogues (particularly 1,25(OH)2-7-dehydrocholesterol and 1,25(OH)2-lumisterol3) have provided definite correlations between binding to the solubilized membrane receptor and the ability to initiate transcaltachia (the rapid hormonal stimulation of calcium transport).