Electrophysiology of cultured parathyroid cells from the goat

The membrane potential and resistance of goat parathyroid (PT) cells in culture were 44.7 +/- 6.8 mV and 503 +/- 218 M omega (mean +/- S.D., n = 24) in 2.4 mM Ca2+ solution. The corresponding values in 0.8 mM Ca2+ solution were 29.2 +/- 12.2 mV and 290 +/- 198 M omega (n = 22). The current/voltage relation showed a pronounced outward rectification for membrane potentials more positive than --40 mV. Current injection produced graded, regenerative responses in half of the penetrated cells. Regenerative responses were also obtained in Na+-free solution, and these responses were reversibly inhibited by the Ca2+ blocker D-600. The results support the notion that PT cells possess voltage sensitive K+ and Ca2+ channels, and that exocytosis of stored PT hormone depends on the influx of extracellular Ca2+ as in other secretory cells.