Bimodal action of [Asu1,7]eel-calcitonin on phosphoinositide hydrolysis in cultured anterior pituitary cells.
[Asu1,7]Eel-calcitonin, a semisynthetic analog of eel-calcitonin displaying high stability and full biological activity, was used to study the effect of calcitonin on phosphoinositide turnover in cultured anterior pituitary cells. Incubation of cells with [Asu1,7]eel-calcitonin produced a slight, concentration-dependent increase in [3H]inositol monophosphate accumulation, without modifying thyrotropin-releasing hormone (TRH)-stimulated phosphoinositide hydrolysis. This effect was correlated with a stimulatory action on prolactin secretion. Conversely, a long-term preincubation with [Asu1,7]eel-calcitonin reduced basal as well as TRH-induced [3H]inositol monophosphate formation. This effect was concentration-dependent, was not due to an increase of cyclic AMP intracellular levels, and was attenuated in the presence of maximally effective concentrations of TRH. Such a long incubation in the presence of [Asu1,7]eel-calcitonin resulted in a marked inhibition of prolactin secretion. The present data confirm and extend previous findings showing an interference of calcitonin with the intracellular cascade consequent to membrane phospholipase C activation and further support a role for calcitonin in the modulation of hormone secretion at the pituitary.
Sortino
M A
MA
School of Medicine, University of Catania, Italy.
Canonico
P L
PL
Clementi
G
G
D000818:Animals; D002116:Calcitonin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004524:Eels; D005260:Female; D006868:Hydrolysis / Q000187:drug effects; D007295:Inositol Phosphates / Q000096:biosynthesis; D007424:Intracellular Fluid / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D014316:Tritium
D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D014316:Tritium; D013973:Thyrotropin-Releasing Hormone; C047872:inositol 2-monophosphate; D002116:Calcitonin; D002772:Cholera Toxin; D000242:Cyclic AMP; D002118:Calcium; C012755:elcatonin