Wong P Y, Huang S J
Department of Physiology, University of Hong Kong.
Exp Physiol. 1990 May;75(3):321-37. doi: 10.1113/expphysiol.1990.sp003407.
Primary monolayer cultures of rat epididymal cells have been shown to secrete chloride and bicarbonate when stimulated with beta-adrenergic agents, humoral agents and vasoactive peptides. The intracellular messengers mediating the secretory response are unknown. In this study intracellular AMP, Ca2+ and inositol phosphates were measured in epididymal monolayers at rest and upon stimulation with various secretory agonists. Adrenaline, forskolin, lysylbradykinin, prostaglandin, endothelin, angiotensin II, antidiuretic hormone and vasoactive intestinal peptide at concentrations that stimulate anion secretion caused a rise in intracellular cyclic AMP. The increase in cyclic AMP by adrenaline was blocked by propranolol but not by phentolamine. Studies of the concentration-effect relationships showed that for adrenaline and endothelin the EC50 for stimulation of cyclic AMP was higher than that for stimulation of anion secretion. None of these agonists affects intracellular Ca2+ concentration and inositol phosphate contents in epididymal monolayers. Ca2+ ionophores A21387, ionomycin and erythrosin B (with irradiation with white light), at concentrations that stimulate anion secretion, also stimulated a rise in intracellular cyclic AMP and concomitantly increased intracellular Ca2+. The increase in cyclic AMP was dependent on extracellular Ca2+. It is not known whether the secretory response to Ca2+ ionophores was mediated by an increase in cell Ca2+ per se, or cyclic AMP. However, it can be concluded that cyclic AMP is the second messenger which mediates the secretory responses to physiological stimuli.
大鼠附睾细胞的原代单层培养物已被证明在受到β-肾上腺素能药物、体液因子和血管活性肽刺激时会分泌氯离子和碳酸氢根离子。介导分泌反应的细胞内信使尚不清楚。在本研究中，测定了附睾单层细胞在静息状态下以及用各种分泌激动剂刺激后的细胞内AMP、Ca2+和肌醇磷酸。肾上腺素、福斯高林、赖氨酰缓激肽、前列腺素、内皮素、血管紧张素II、抗利尿激素和血管活性肠肽在刺激阴离子分泌的浓度下可引起细胞内环磷酸腺苷（cAMP）升高。肾上腺素引起的cAMP升高被普萘洛尔阻断，但未被酚妥拉明阻断。浓度-效应关系研究表明，对于肾上腺素和内皮素，刺激cAMP的半数有效浓度（EC50）高于刺激阴离子分泌的EC50。这些激动剂均不影响附睾单层细胞内的Ca2+浓度和肌醇磷酸含量。Ca2+离子载体A21387、离子霉素和赤藓红B（白光照射）在刺激阴离子分泌的浓度下，也刺激细胞内cAMP升高，并伴随细胞内Ca2+增加。cAMP的升高依赖于细胞外Ca2+。尚不清楚对Ca2+离子载体的分泌反应是由细胞内Ca2+本身增加介导的，还是由cAMP介导的。然而，可以得出结论，cAMP是介导对生理刺激分泌反应的第二信使。
