Potassium currents and effects of vitamin D-3 metabolites and cyclic GMP in rat osteoblastic cells.
A K+ current (IK1), activated by depolarization above -20 mV, showing voltage-dependent inactivation within a few seconds and reduced by 40% by 1 mM TEA, was observed in all cells. In a few cells, we also observed a progressive K(+)-current increase during cell dialysis. The developing current (IK2) was not sensitive to 1 mM TEA and did not inactivate. It was detectable over the whole voltage range and slowly increased during 10 s depolarizations. 1,25-(OH)2D3 and 24,25-(OH)2D3 did not affect IK1, but induced a small K(+)-current increase in some cells showing no IK2. This effect was not mimicked by cyclic GMP analogs which, on the contrary, induced a K(+)-current decrease. 24,25-(OH)2D3 (even at 10(-11)M, but not 1,25-(OH)2D3, strongly reduced IK2. The results further document the diversity of voltage-gated currents of osteoblastic cells, confirm the existence of immediate effects of vitamin D-3 metabolites, which are independent of classical 1,25-(OH)2D3 receptors.
Laboratoire de Neurobiologie, Ecole Normale Supérieure, Paris, France.
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Chesnoy-Marchais
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Fritsch
D015650:24,25-Dihydroxyvitamin D 3 / Q000494:pharmacology*; D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000494:pharmacology*; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000502:physiology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D015221:Potassium Channels; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D013757:Tetraethylammonium Compounds; D015650:24,25-Dihydroxyvitamin D 3; D002117:Calcitriol; D006152:Cyclic GMP