Ca2(+)-channel agonist BAY K8644 mimics 1,25(OH)2-vitamin D3 rapid enhancement of Ca2+ transport in chick perfused duodenum.
To further understand the molecular mechanism by which 1,25(OH)2-vitamin D3 [1,25(OH2D3] rapidly stimulates intestinal calcium transport (termed "transcaltachia"), the effect of the calcium channel agonist BAY K8644 was studied in vascularly perfused duodenal loops from normal, vitamin D-replete chicks. BAY K8644, 2 mu M, was found to stimulate 45Ca2+ transport from the lumen to the vascular effluent to the same extent as physiological levels of 1,25(OH)2D3. The sterol and the Ca2+ channel agonist both increased 45Ca2+ transport 70% above control values within 2 min and 200% after 30 min of vascular perfusion. The effect of the Ca2+ channel agonist was dose dependent. Also, 1,25(OH)2D3-enhanced transcaltachia was abolished by the calcium channel blocker nifedipine. Collectively, these results suggest the involvement of 1,25(OH)2D3 in the activation of basal lateral membrane Ca2+ channels as an early effect in the transcaltachic response.
Department of Biochemistry, University of California, Riverside 92521.
A R
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de Boland
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I
Nemere
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Norman
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002122:Calcium Chloride / Q000378:metabolism; D002132:Calcium Radioisotopes; D002645:Chickens; D004386:Duodenum / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D009130:Muscle, Smooth / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D010477:Perfusion; D012016:Reference Values; D014808:Vitamin D Deficiency / Q000378:metabolism
D002132:Calcium Radioisotopes; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002117:Calcitriol; D009543:Nifedipine; D002122:Calcium Chloride; D002118:Calcium