Thyrotrophin and prostaglandin E2 increase calmodulin levels and cyclic AMP phosphodiesterase activity in cultured porcine thyroid cells |
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| Authors: | N Takasu T Yamada Y Shimizu |
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| Affiliation: | Department of Gerontology, Endocrinology and Metabolism, School of Medicine, Shinshu University, Nagano-ken, Japan. |
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| Abstract: | Thyrotrophin (TSH) and prostaglandin E2 (PGE2) increased cellular cyclic AMP (cAMP), calmodulin levels and cAMP phosphodiesterase activity in cultured porcine thyroid cells. Dibutyryl cAMP (dbcAMP), a stable analogue of cAMP, increased calmodulin levels and cAMP phosphodiesterase activity. These results indicate that TSH- and PGE2-stimulated increases in calmodulin are mediated by cAMP. This increased concentration of calmodulin in turn stimulates cAMP phosphodiesterase. Double reciprocal plots of cAMP hydrolysis yielded two apparent Michaelis constants (Km); the lower in the 1 mumol/l and the higher in the 10 mumol/l range. Thyrotrophin, PGE2 and dbcAMP increased the values of maximal velocity without changing the Km values. |
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