Effects of 1,25- and 24,25-dihydroxycholecalciferol on parathyroid hormone release from human parathyroid cells in vitro.
The effects of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) and 24,25-dihydroxycholecalciferol (24,25-(OH)2D3) on parathyroid hormone (PTH) release from human parathyroid cells were investigated using an in vitro system of dispersed cells. The cells were obtained from 7 patients with primary hyperparathyroidism (HPT) and adenoma, 4 patients with primary HPT due to hyperplasia and 2 patients with parathyroid hyperplasia secondary to chronic renal failure. The dispersed cells were incubated in tissue culture medium at low, normal and high external calcium concentrations for 2-16 h. There was a gradual suppression of PTH release (5-55%) when the calcium concentration in the medium was increased from 0.5 to 3.0 mM, thus indicating retained regulation of hormone release. The addition of 1,25-(OH)2D3 in concentrations of 0.1 and 1 ng/ml and of 24,25-(OH)2D3 in concentrations of 1.0 and 10 ng/ml during the incubations did not further affect the amount of PTH released by the cells. The concentrations of the different vitamin D metabolites tested closely correspond to levels observed under normal physiological conditions and during treatment with high doses of vitamin D in vivo. Thus, the findings contradict the idea of any direct short-term regulatory effect of either 1,25-(OH)2D3 or 24,25-(OH)2D3 on the secretion of PTH from hyperfunctioning human parathyroid tissue.
D015650:24,25-Dihydroxyvitamin D 3; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D003470:Culture Media; D046508:Culture Techniques; D004100:Dihydroxycholecalciferols / Q000494:pharmacology*; D006801:Humans; D006934:Hypercalcemia; D006961:Hyperparathyroidism / Q000503:physiopathology; D010280:Parathyroid Glands / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000378:metabolism*; D013997:Time Factors
D003470:Culture Media; D004100:Dihydroxycholecalciferols; D010281:Parathyroid Hormone; D015650:24,25-Dihydroxyvitamin D 3; D002117:Calcitriol; D002118:Calcium