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Regulation of parathyroid hormone gene expression and peptide secretion in human parathyroid cells

Liu J, Kahri AI, Teppo A-M, Voutilainen R. Regulation of parathyroid hormone gene expression and peptide secretion in human parathyroid cells. Eur J Endocrinol 1994;130:394–401. ISSN 0804–4643

In cell cultures prepared from human parathyroid adenomas, parathyroid hormone (PTH) mRNA expression decreased slowly. During short-term incubations (less than 24), a low calcium concentration (0.5 mmol/l) and protein kinase C activator TPA (12-O-tetradecanoyl phorbol 13-acetate) (160 nmol/l) increased PTH secretion (60%; p <0.05), while a high extracellular calcium concentration (2.5 mmol/l) reduced PTH secretion (60%; p<0.05), The TPA could block the inhibitory effect of a high calcium level on PTH peptide secretion. All these agents had no effect on PTH mRNA accumulation in short-term experiments. In long-term cultures (more than 24 h), a low calcium level increased and a high calcium level reduced both PTH mRNA (85 and 34%; p <0.05) and peptide secretion (140 and 80%; p <0.05), respectively. The TPA reduced PTH mRNA accumulation down to 30% (p<0.05) and PTH secretion down to 14% (p<0.05) in a time- and dose-dependent fashion. The TPA also reversed the stimulatory effect of hypocalcemia on PTH mRNA accumulation and peptide secretion. Protein kinase C inhibitors staurosporine (100 nmol/l) and H-7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride) (50 µmol/l) had similar effects to TPA on PTH gene expression and peptide secretion in long-term cultures. The results support the hypothesis that extracellular calcium regulates PTH mRNA accumulation and PTH secretion via protein kinase C.

Raimo Voutilainen, Department of Pathology, PO Box 21 (Haartmaninkatu 3), SF-00014 University of Helsinki, Finland