ABSENCE OF CALCITRIOL-MEDIATED NONGENOMIC ACTIONS IN ISOLATED INTESTINAL-CELLS OF THE DAMARA MOLE-RAT (CRYPTOMYS DAMARENSIS)

Calcitriol [1,25(OH)(2)D-3] actions on intestinal calcium transport in volve genomic and nongenomic pathways. Whether nongenomic 1,25(OH)(2)D -3-mediated actions are employed was investigated using isolated intes tinal epithelial cells of naturally vitamin D-deficient underground-dw elling damara mole-rats (Cryptomys damarensis). 1,25(OH)(2)D-3-mediate d nongenomic pathways of intestinal calcium uptake, measured by openin g of 1,25(OH)(2)D-3-activated voltage-sensitive Ca2+ channels (VSGC), did not occur. Rapid (1 min) Ca-45(2+) transmembrane influx in intesti nal cells was not significantly increased by the addition of 1,25(OH)( 2)D-3 (at concentrations from 10(-12) to 10(-6) nM), when compared to opening of VSCC in the presence of a depolarizing (elevated K+) buffer . Furthermore, even after 30 min calcium uptake was not significantly enhanced by the hormone. These findings support earlier reports that d uodenal calcium absorption is independent of vitamin D and is a highly adaptive feature of a subterranean existence. (C) 1994 Academic Press , Inc.