Postnatal alterations of mechanisms of signal transduction in rat salivary glands

研究了出生后大鼠腮腺功能的改变与β肾上腺素受体-腺苷酸环化酶系统的关系。1周龄大鼠组织对异丙肾上腺素（IPR）有反应并引起淀粉酶分泌。淀粉酶分泌IPR组织的EC_<50>值比成年大鼠高10倍。组织也对forskolin（FOR）有反应，并显著引起淀粉酶分泌。然而，组织对FOR的分泌反应在发育过程中下降。[^3H]二氢阿普萘洛尔（DHA）的结合实验表明，该配体在3日龄大鼠腮腺组织中已经检测到特异性结合，Bmax值稳步上升，直到出生后4周才趋于成年大鼠组织的Bmax值。1、8周龄大鼠组织中[^3H]DHA结合IPR的IC_<50>值为890 （]SY.+-）。[) 74.2和3.5 (]SY.+-。[)分别为0.8 mm。而心得安在发育过程中没有表现出任何变化。1周龄大鼠组织中c-AMP的含量与成年大鼠组织中c-AMP的含量相同。IPR对成年大鼠组织的增加率是1周龄大鼠的2倍。FOR也引起了c-AMP含量的显著增加，但在发育和淀粉酶分泌过程中，反应明显减弱。[^<35 b> S]GTPgammaS结合实验显示，1周龄大鼠组织中G蛋白具有GTP结合能力。在发育过程中，组织中特异性[^<35>S]GTPgammaS结合的Bmax值稳步增加，在出生后4周达到平稳期。Gs蛋白和Gi蛋白的GTP结合能力均表现出相同的发育增强。这些结果表明，大鼠腮腺组织中β -肾上腺素能-腺苷酸环化酶系统的功能在发育过程中显著增强，β -肾上腺素能刺激在成年大鼠中诱导淀粉酶分泌的效果更佳。少

The postnatal alteration of the function of rat parotid glands was studied in relation to that of BETA adrenoceptor-adenylate cyclase system. The tissues of 1-week-old rats responded to isoproterenol(IPR) and caused amylase secretion. The EC_<50> value of the tissues for IPR in amylase secretion was ten time higher than that of adult rats. The tissues also responded to forskolin(FOR) and markedly caused amylase secretion. However, the secretory response of the tissues to FOR decreased during development. Binding experiments of [^3H]dihydroalprenolol(DHA) show that the specific binding of the ligand was already detected in parotid tissues of 3-day-old rats and Bmax value increased steadily until 4 week after birth when it leveled off to that of the tissues of adult rats. The IC_<50> values of IPR for [^3H]DHA binding in the tissues of 1-and 8-week old rats were 890 (〕SY.+-.〔) 74.2 and 3.5 (〕SY.+-.〔) 0.8muM, respectively. But the value of propranolol did not show any changes during devel … More opment. The c-AMP content in the tissues of 1-week-old rats also increased by the treatment with IPR as observed in adult rat tissues. The increasing ratio in the tissues of adult rats by IPR was twice as that of 1-week-old rats. FOR also caused remarkable increases in c-AMP content, but the response markedly decreased during development and paralleled amylase secretion. Binding experiments of [^<35>S]GTPgammaS showed the presence of GTP binding capacity of G proteins in the tissues of 1-week-old rats. The Bmax value of specific [^<35>S]GTPgammaS binding in the tissues in creased steadily during development, reaching plateau at 4 weeks after birth. The GTP binding capacities of Gs proteins and Gi proteins showed the same developmental increases.These results show that the function of beta-adrenoceptor-adenylate cyclase system in rat parotid tissues is markedly enhanced during development and the superior efficacy of the beta-adrenergic stimuli for the induction of amylase secretion is to be found in adult rats. Less