Dye and electric coupling between osteoblast-like cells in culture.

Primary cultures of osteoblast-like cells (OB) derived from calvarial fragments of newborn rats and juvenile guinea pigs formed numerous gap junctions between neighboring cells in vitro. Intracellular injection of Lucifer yellow led to a staining of up to 30 adjacent cells. Parallel intracellular recordings showed that amplitudes of stimulated membrane potential changes (4-5 mV) were closely related between coupled cells. The coupling factor, which was derived from the ratio of these amplitudes, ranged between 0.1 and 0.8. The coupling factor (1) was not dependent on the membrane potential or the injected current strength; (2) strong acidosis (pH < 6.6) and hypercapnia (pCO2 > 80 mm Hg) did not affect electric or dye coupling; (3) elevation of intracellular cAMP level was ineffective; (4) rise of the extra- and intracellular Ca2+ concentration did not effect the electric coupling; (5) the anticonvulsant drugs carbamazepine and phenytoin impaired the coupling factor up to 59%. The findings show that cell-cell communication between OB via gap junctions proved stable under various conditions which, in other tissues, were found to reduce the coupling strength of gap junctions.