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Relationship between external and cytoplasmic calcium concentrations, parathyroid hormone release and weight of parathyroid glands in human hyperparathyroidism

Relationship between external and cytoplasmic calcium concentrations, parathyroid hormone release... ABSTRACTParathyroid hormone (PTH) release and cytoplasmic calcium concentrations were investigated at ambient calcium concentrations of 0·5–3·0 mmol/l in dispersed parathyroid cells from 44 hypercalcaemic patients with primary or uraemic hyperparathyroidism (HPT). In comparison with parathyroid cells from adult cattle, release of PTH by human preparations was reduced and values of the ambient calcium concentration causing half-maximal inhibition of PTH release (median effective dose, ED50) were significantly increased. Half-maximal inhibition of PTH release was obtained with concentrations of cytoplasmic calcium almost identical to the concentrations of ionized calcium in the plasma of the individual patients. Cytoplasmic concentrations of calcium in the parathyroid cells were inversely related to release of PTH. Concentrations of cytoplasmic calcium were significantly lower in human than in bovine cells and the ED50 for ambient calcium increase on cytoplasmic calcium was raised to the same extent as the ED50 for ambient calcium inhibition of PTH release in human compared with bovine cells. The magnitude of the increased ED50 for ambient calcium inhibition of PTH release and increase of cytoplasmic calcium concentration was similar in adenomas and sporadic as well as hereditary primary hyperplasias, but the secretion was the least aberrant in uraemic hyperplasias, although they had by far the largest glandular mass. Serum concentrations of total calcium before surgery correlated with the ED50 for ambient calcium effects of PTH release and cytoplasmic calcium, but not with glandular weight. These findings demonstrate a universally abnormal regulation of cytoplasmic calcium in HPT and its importance for PTH release, and that disturbance of cytoplasmic calcium rather than the increased glandular mass contributes to the hypercalcaemia in adenomatous and hyperplastic HPT.J. Endocr. (1988) 116, 457–464 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Endocrinology Bioscientifica

Relationship between external and cytoplasmic calcium concentrations, parathyroid hormone release and weight of parathyroid glands in human hyperparathyroidism

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Publisher
Bioscientifica
Copyright
Copyright © 1988 The Authors. All Rights Reserved.
ISSN
0022-0795
eISSN
1479-6805
DOI
10.1677/joe.0.1160457
Publisher site
See Article on Publisher Site

Abstract

ABSTRACTParathyroid hormone (PTH) release and cytoplasmic calcium concentrations were investigated at ambient calcium concentrations of 0·5–3·0 mmol/l in dispersed parathyroid cells from 44 hypercalcaemic patients with primary or uraemic hyperparathyroidism (HPT). In comparison with parathyroid cells from adult cattle, release of PTH by human preparations was reduced and values of the ambient calcium concentration causing half-maximal inhibition of PTH release (median effective dose, ED50) were significantly increased. Half-maximal inhibition of PTH release was obtained with concentrations of cytoplasmic calcium almost identical to the concentrations of ionized calcium in the plasma of the individual patients. Cytoplasmic concentrations of calcium in the parathyroid cells were inversely related to release of PTH. Concentrations of cytoplasmic calcium were significantly lower in human than in bovine cells and the ED50 for ambient calcium increase on cytoplasmic calcium was raised to the same extent as the ED50 for ambient calcium inhibition of PTH release in human compared with bovine cells. The magnitude of the increased ED50 for ambient calcium inhibition of PTH release and increase of cytoplasmic calcium concentration was similar in adenomas and sporadic as well as hereditary primary hyperplasias, but the secretion was the least aberrant in uraemic hyperplasias, although they had by far the largest glandular mass. Serum concentrations of total calcium before surgery correlated with the ED50 for ambient calcium effects of PTH release and cytoplasmic calcium, but not with glandular weight. These findings demonstrate a universally abnormal regulation of cytoplasmic calcium in HPT and its importance for PTH release, and that disturbance of cytoplasmic calcium rather than the increased glandular mass contributes to the hypercalcaemia in adenomatous and hyperplastic HPT.J. Endocr. (1988) 116, 457–464

Journal

Journal of Endocrinology – Bioscientifica

Published: Mar 1, 1988

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