Ishikawa Y, Amano I, Chen C, Ishida H
Department of Pharmacology, Tokushima University School of Dentistry, Japan.
Res Exp Med (Berl). 1992;192(4):231-40. doi: 10.1007/BF02576279.
Diurnal changes in the neurotransmitter receptors are important for studying the receptor function in neurophysiology. The purpose of this study is to gain an insight into the regulatory mechanisms of the diurnal variation of amylase secretion. Rat salivary amylase levels showed a diurnal variation with two peaks, a marked peak at 13 h and a lesser peak at 21 h. This increase in salivary amylase levels was completely inhibited by pretreatment of rats with the beta-adrenergic antagonist propranolol, but not by the alpha-adrenergic antagonist phentolamine. Amylase level in parotid tissue homogenate also showed a diurnal change, but there was only one peak, at 13 h. The number of maximal binding sites (Bmax) for [3H]dihydroalprenolol (DHA) in parotid membranes showed a diurnal variation with two marked peaks at 13 and 21 h, but the affinity of parotid beta-adrenoceptors for agonists or antagonists did not show any diurnal changes. Phosphorylation of nuclear non-histone proteins in the rat parotid gland showed diurnal variation with two marked peaks at 13 and 21 h. These results indicate that a diurnal variation in the number of rat parotid beta-adrenoceptors, which is presumably regulated by gene expression, is coupled with a change in salivary amylase secretion.
神经递质受体的昼夜变化对于研究神经生理学中的受体功能很重要。本研究的目的是深入了解淀粉酶分泌昼夜变化的调节机制。大鼠唾液淀粉酶水平呈现昼夜变化，有两个峰值，一个在13时的明显峰值和一个在21时的较小峰值。唾液淀粉酶水平的这种升高被用β-肾上腺素能拮抗剂普萘洛尔预处理大鼠完全抑制，但未被α-肾上腺素能拮抗剂酚妥拉明抑制。腮腺组织匀浆中的淀粉酶水平也呈现昼夜变化，但只有一个峰值，在13时。腮腺膜中[3H]二氢阿普洛尔（DHA）的最大结合位点（Bmax）数量呈现昼夜变化，在13和21时有两个明显峰值，但腮腺β-肾上腺素能受体对激动剂或拮抗剂的亲和力未显示任何昼夜变化。大鼠腮腺中核非组蛋白的磷酸化呈现昼夜变化，在13和21时有两个明显峰值。这些结果表明，大鼠腮腺β-肾上腺素能受体数量的昼夜变化，可能由基因表达调节，与唾液淀粉酶分泌的变化相关。
