Stimulating Effects of Dopamine on Chloride Transport Across the Rat Caudal Epididymal Epithelium in Culture

• Published in: Biology of reproduction 2009-01, Vol.80 (1), p.13-23
• Main Authors: DU, Jian-Yang, ZUO, Wu-Lin, RUAN, Ye-Chun, YANG, Zi-Huan, CHEN, Min-Hui, CHEN, Si-Liang, SHENG LI, WU, Zhong-Luan, HUI XIANG, ZHOU, Wen-Liang
• Format: Article
• Language: English
• Subjects: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid - pharmacology; Adrenergic Antagonists - pharmacology; Animals; Biological and medical sciences; Cell physiology; Chloride Channels - antagonists & inhibitors; Chloride Channels - metabolism; Chlorides - metabolism; Dopamine - pharmacology; Enzyme Inhibitors - pharmacology; Epididymis - drug effects; Epididymis - metabolism; Epididymis - secretion; Fundamental and applied biological sciences. Psychology; Imines - pharmacology; In Vitro Techniques; Male; Molecular and cellular biology; ortho-Aminobenzoates - pharmacology; Patch-Clamp Techniques; Phentolamine - pharmacology; Propranolol - pharmacology; Rats; Rats, Sprague-Dawley; Signal transduction
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod.108.068346

The present study investigated the effects of dopamine on chloride transport across cultured rat caudal epididymal epithelium. The results showed that dopamine induced a biphasic short-circuit current (Isc) in a concentration-dependent manner. The dopamine-induced response consisted of an initial rapid spike followed by a sustained phase. The alpha and beta adrenoreceptor inhibitors, phentolamine and propranolol, inhibited the initial spike and the sustained phase, respectively, suggesting a contribution of adrenergic receptors. The response was almost abolished by removing the extracellular Cl − , suggesting that the dopamine-induced short-circuit current is primarily a Cl − current. The response was inhibited by the apical Cl − channel blocker, diphenylamine-dicarboxylic acid, and the Ca 2+ -activated Cl − channel blocker, disulfonic acid stilbene, indicating that Cl − may pass through two types of Cl − channels on the apical side. Preloading monolayers with the intracellular Ca 2+ chelator BAPTA/AM abolished the initial spike and greatly reduced the second phase in the Isc response to dopamine. Pretreating the monolayers with an adenylate cyclase inhibitor, MDL12330A, inhibited all of the second Isc response and part of the initial spike. Also, characteristics of the Cl − currents induced by dopamine were observed in whole-cell patch-clamp recording. The increases of intracellular cAMP and Ca 2+ induced by dopamine were also measured. The results suggest that extracellular dopamine activates Ca 2+ -dependent and cAMP-dependent regulatory pathways, leading to activation of both Ca 2+ -dependent and cAMP-dependent Cl − conductances in epididymal epithelial cells.