R. Buffenstein et al., ABSENCE OF CALCITRIOL-MEDIATED NONGENOMIC ACTIONS IN ISOLATED INTESTINAL-CELLS OF THE DAMARA MOLE-RAT (CRYPTOMYS DAMARENSIS), General and comparative endocrinology, 95(1), 1994, pp. 25-30
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.