1. Vitamin D metabolite effects on membrane potential and potassium intracellular activity in rabbit cartilage
- Author
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Aleksander Edelman, Cl, Thil, Garabedian M, Jj, Plachot, Guillozo H, Fritsch J, Sr, Thomas, and Balsan S
- Subjects
Male ,Time Factors ,24,25-Dihydroxyvitamin D 3 ,Hypertrophy ,In Vitro Techniques ,Membrane Potentials ,Cartilage ,Calcitriol ,Dihydroxycholecalciferols ,Potassium ,Animals ,Growth Plate ,Rabbits ,Ouabain ,Microelectrodes ,Cell Division - Abstract
In rabbit cartilage growth plates, the membrane potential, Vm, and potassium intracellular activities, alpha iK, were determined in order to study the effects of long-term (48 h) and short-term (1-2 min) exposures to vitamin D metabolites. Results are as follows: (i) in proliferative cells, Vm was -55.6 +/- 0.2 mV, n = 30, and alpha ik = 50.8 +/- 4.2 mM, n = 22; (ii) in hypertrophic cells, Vm was -35.5 +/- 0.8 mV, n = 88, and alpha iK = 85.1 +/- 5.4 mM, n = 20; (iii) Vm (-44.0 +/- 1.0 mV, n = 33) and alpha iK (114.7 +/- 8.7 mM, n = 14) were increased in metatarsal hypertrophic cells incubated with 10(-10)M of 1,25(OH)2D3 but were unaffected by the presence of 24,25(OH)2D3; (iv) an hyperpolarization of Vm was observed after short-term exposure of the hypertrophic cells to 10(-10)M of 1,25(OH)2D3 (-2.2 +/- 0.2 mV, n = 34) and 24,25(OH)2D3 (-2.2 +/- 0.7 mV, n = 17) but not to 25(OH)D3 (+0.3 +/- 0.8 mV, n = 10).