CA2-INDUCED CA2+ OSCILLATIONS IN PARATHYROID CELLS()

Parathyroid cells from patients with hyperparathyroidism were first cu ltured in a growth cocktail supplemented version of Dulbecco's MEM/F12 medium and then used for measurements of the cytoplasmic Ca2+ concent ration ([Ca2+](i)). Elevation of extracellular Ca2+ from 0.5 to 1.5-3 mM often triggered rhythmic oscillations of [Ca2+](i). Whereas the amp litude of the oscillations remained constant their frequency (0.4-2.6 /min) increased with the Ca2+ concentration and there was sometimes tr ansformation into sustained increase of [Ca2+](i) at the highest extra cellular Ca2+ concentration. The oscillations were abolished by the in organic Ca2+ channel blocker Ce3+ and by K+ depolarisation, which lowe red [Ca2+](i), as well as by thapsigargin, an inhibitor of the intrace llular Ca2+-pumping ATPase. The data indicate that extracellular Ca2can trigger [Ca2+](i) oscillations in parathyroid cells, dependent on mobilisation of the ion from intracellular Ca2+ stores and on influx t hrough non-voltage dependent channels. (C) 1995 Academic Press, Inc .