Sortino M A, Canonico P L, Clementi G
School of Medicine, University of Catania, Italy.
Eur J Pharmacol. 1991 Aug 14;207(4):345-50. doi: 10.1016/0922-4106(91)90009-7.
[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.
[Asu1,7]鳗鱼降钙素是鳗鱼降钙素的一种半合成类似物，具有高稳定性和完全的生物活性，被用于研究降钙素对培养的垂体前叶细胞中磷酸肌醇代谢的影响。用[Asu1,7]鳗鱼降钙素孵育细胞会使[3H]肌醇单磷酸积累略有浓度依赖性增加，而不改变促甲状腺激素释放激素（TRH）刺激的磷酸肌醇水解。这种作用与对催乳素分泌的刺激作用相关。相反，用[Asu1,7]鳗鱼降钙素进行长期预孵育会降低基础以及TRH诱导的[3H]肌醇单磷酸形成。这种作用是浓度依赖性的，不是由于细胞内环磷酸腺苷水平升高所致，并且在存在最大有效浓度的TRH时会减弱。在[Asu1,7]鳗鱼降钙素存在下进行这样的长时间孵育会导致催乳素分泌受到明显抑制。目前的数据证实并扩展了先前的研究结果，表明降钙素会干扰膜磷脂酶C激活后随之而来的细胞内级联反应，并进一步支持降钙素在垂体激素分泌调节中的作用。
