title: Vitamin D3 metabolites increase [Ca2+]i in rabbit renal proximal straight tubule cells.
abstract: Vitamin D metabolites exert both acute and chronic influences on proximal tubule function. To further evaluate vitamin D action on the kidney, we examined the immediate effects of vitamin D metabolites on cytoplasmic calcium ion concentration [( Ca2+]i), using fura-2 and patch-clamp method in cultured proximal straight tubule cells of rabbit kidney. 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] and 25-hydroxyvitamin D3 [25(OH)D3] evoked a transient rise in [Ca2+]i, and 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] caused a sustained rise in [Ca2+]i; all effects were dose dependent. [Ca2+]i transient, evoked by 1,25(OH)2D3 alone, was abolished in Ca(2+)-free media. Pretreatment of cells in Ca(2+)-free media with caffeine (4 mM) or ryanodine (1 microM) to deplete Ca2+ store of endoplasmic reticulum or with TMB-8 (5 mM) to block Ca2+ release from storage blunted the effect of 25(OH)D3 on [Ca2+]i but not of 24,25(OH)2D3. Data were also supported by activities of Ca-dependent K channel and show that these three vitamin D metabolites in pharmacological doses increase [Ca2+]i of proximal tubule cells from different sources.
authors.affiliation: Second Department of Internal Medicine, Jikei University School of Medicine, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Suzuki
authors.forename: S
authors.initials: S
authors.lastname: Kurihara
authors.forename: Y
authors.initials: Y
authors.lastname: Kawaguchi
authors.forename: O
authors.initials: O
authors.lastname: Sakai
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3 / Q000494:pharmacology; D000818:Animals; D002112:Calcifediol / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002762:Cholecalciferol / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D008297:Male; D009994:Osmolar Concentration; D015221:Potassium Channels / Q000378:metabolism; D011817:Rabbits
chemical_list: D015221:Potassium Channels; D002762:Cholecalciferol; D015650:24,25-Dihydroxyvitamin D 3; D002112:Calcifediol; D002118:Calcium