Combined effect of calcitonin and glucocorticoid hormone on calcium content of cultured bone cells.

The combined effect of calcitonin and triamcinolone acetonide on Ca2+ content in cultured bone cells was studied. Cultures were first preincubated with 45Ca for 24 hrs thus achieving a steady state between the extracellular and intracellular 45Ca2+. Calcitonin was added for 24 hrs and subsequently, triamcinolone acetonide was added for time intervals ranging from 1 to 24 hrs. Calcitonin induced a significant increase in the content of cellular exchangeable Ca2+. When triamcinolone was added to cultures pretreated with calcitonin a marked efflux activity was noted. Concomitant ultrastructural histochemical examinations, using the K-pyroenthymonate fixation method, further substantiated the above finding: calcitonin treated cells revealed increased number of Ca-pyroenthymonate precipitates, whereas the combined treatment led to the disappearance of such Ca-aggregates.