Absence of calcitriol-mediated nongenomic actions in isolated intestinal cells of the damara mole-rat (Cryptomys damarensis).
Calcitriol [1,25(OH)2D3] actions on intestinal calcium transport involve genomic and nongenomic pathways. Whether nongenomic 1,25(OH)2D3-mediated actions are employed was investigated using isolated intestinal epithelial cells of naturally vitamin D-deficient underground-dwelling damara mole-rats (Cryptomys damarensis). 1,25(OH)2D3-mediated nongenomic pathways of intestinal calcium uptake, measured by opening of 1,25(OH)2D3-activated voltage-sensitive Ca2+ channels (VSCC), did not occur. Rapid (1 min) 45Ca2+ transmembrane influx in intestinal cells was not significantly increased by the addition of 1,25(OH)2D3 (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 duodenal calcium absorption is independent of vitamin D and is a highly adaptive feature of a subterranean existence.
Buffenstein
R
R
Department of Physiology, Medical School, University of the Witwatersrand, Johannesburg, South Africa.
Sergeev
I N
IN
Pettifor
J M
JM
D000818:Animals; D002117:Calcitriol / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004848:Epithelium / Q000502:physiology; D005260:Female; D007421:Intestine, Small / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D008297:Male; D012377:Rodentia / Q000502:physiology*; D014807:Vitamin D / Q000378:metabolism / Q000494:pharmacology
D014807:Vitamin D; D002117:Calcitriol; D002118:Calcium