title: Electrophysiological properties of osteoblastlike cells from the cortical endosteal surface of rabbit long bones.
abstract: The mean transmembrane potential of cultured osteoblastlike cells isolated from the cortical endosteal surface of rabbit long bones was -16.9 +/- 0.64 mV (n = 335). Elevation of potassium concentration in medium caused a decrease in potential. As the external concentration of potassium reached 15 mmol/liter and above, there was a linear relationship between the potassium concentration in log scale and the membrane potential with a slope of -13 mV per 10-fold change in external potassium concentration. Dibutyryladenosine 3',5'-cyclic monophosphate, parathyroid extract, hydrocortisone, and sodium fluoride all depolarized the membrane of osteoblast-like cells after both short (1-2 h) and long (24 h) exposures at suitable doses, whereas calcitonin and prostaglandin E2 hyperpolarized the membrane after long exposures. The Na+, K+ and Cl- concentrations of cultured osteoblastlike cells were 0.538, 0.984, and 0.358 mmol/g protein or 52.6, 96.3, and 35.0 mmol/liter cell water, respectively. The protein content of these cells was 8.18 +/- 0.6 g/100 g cells and the water content was 83.7 g/100 g cells. The above-mentioned chemical and hormonal preparations in doses that produced significant changes in the membrane potential of these cultured cells did not alter their electrolyte or protein contents 24 h after exposure. Intracellular pH of cultured osteoblastlike cells as determined by [14C]-dimethyloxazolidine-2,4-dione and 3H2O averaged 7.03 +/- 0.11 when the pH of culture medium was maintained at 7.4. Calculations based on the values for the membrane potential and the electrolyte concentrations observed in this study indicate that Na+, and H+, and Cl- are actively transported out of the cells and K+ into the cells.
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000166:cytology; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D006728:Hormones / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000187:drug effects; D010006:Osteoblasts / Q000502:physiology*; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism
chemical_list: D002712:Chlorides; D006728:Hormones; D003994:Bucladesine; D012964:Sodium; D011188:Potassium