Effect of thyroidectomy on intracellular amount and distribution of exchangeable Ca2+ in isolated rat liver cells.

The effect of thyroidectomy and replacement therapy on intracellular calcium was studied in isolated rat liver cells. The cells were first loaded with 45Ca and the efflux of isotope followed for 4 h. The cells maintained their viability during this period as judged from staining with trypan blue and rate of respiration. Two different time constants could be resolved by the peeling method. The experiments showed that thyroidectomy markedly reduced the pool of calcium with the slowest turnover while the other pool remained unchanged. Administration of triiodothyronine (T3) to the thyroidectomized animals 48 h before the experiment normalized the rate of respiration but did not restore the slow turnover pool of calcium.