In vitro suppression of parathyroid hormone secretion by 22-oxa-calcitriol in human parathyroid hyperplasia due to uraemia

SUMMARY: 22-oxa-calcitriol (OCT), a vitamin D analogue, suppresses parathyroid hormone (PTH) secretion and has less calcaemic activity than 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] in vivo. In this study, we evaluated the effect of OCT on PTH secretion in vitro using human hyperplastic parathyroid tissue obtained during surgery for advanced renal hyperparathyroidism and normal bovine parathyroid glands to compare the effects of 1,25(OH)2D3. 22-oxa-calcitriol suppressed PTH secretion by nodular hyperplastic parathyroid tissue and normal bovine tissue in a dose dependent manner, the same as 1,25(OH)2D3. We showed the additive effect of extracellular calcium level on suppression of PTH secretion by OCT and 1,25(OH)2D3. These results suggest that OCT suppresses PTH secretion, the same as 1,25(OH)2D3 not only in normal parathyroid cells but also on hyperplastic parathyroid cells.