Functional dedifferentiation of parathyroid cells results both from a defective regulation and action of cytoplasmic Ca2+.
Monolayer culture of bovine parathyroid cells for 24 hours resulted in a right-shift of the dose-effect relationships for Ca2+-inhibition of parathyroid hormone (PTH) release and the dependence of the cytoplasmic Ca2+ concentration (Cai2+) on extracellular Ca2+ as well as in a less suppressible hormone release. After 4 days of culture, hormone secretion was almost non-suppressible and Cai2+ increased poorly in response to a rise in extracellular Ca2+. Ionomycin, a Ca2+ ionophore, raised Cai2+, but there was only a small inhibition of PTH release and the correlation between Cai2+ and secretion was weak. A deteriorated Cai2+ regulation and a decreased inhibitory action of cytoplasmic Ca2+ on PTH release were also found in cells from human parathyroid adenomas. Functional dedifferentiation of the parathyroid cell thus results from both defective regulation and action of cytoplasmic Ca2+.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002417:Cattle; D002454:Cell Differentiation; D002478:Cells, Cultured; D003593:Cytoplasm / Q000502:physiology; D004987:Ethers / Q000494:pharmacology; D005110:Extracellular Space / Q000502:physiology; D006801:Humans; D015759:Ionomycin; D010280:Parathyroid Glands / Q000166:cytology / Q000502:physiology*; D010281:Parathyroid Hormone / Q000378:metabolism*
D004987:Ethers; D010281:Parathyroid Hormone; D015759:Ionomycin; D002118:Calcium