Biphasic short-circuit current response to noradrenaline mediated by Ca2+ and cAMP in cultured rat epididymal epithelium

• Published in: Pflügers Archiv 1994-03, Vol.426 (5), p.396-401
• Main Authors: LEUNG, A. Y. H, WONG, P. Y. D
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Calcium - pharmacology; Calcium-Transporting ATPases - antagonists & inhibitors; Cells, Cultured; Cyclic AMP - analysis; Cyclic AMP - pharmacology; Dose-Response Relationship, Drug; Egtazic Acid - analogs & derivatives; Egtazic Acid - pharmacology; Epididymis - chemistry; Epididymis - cytology; Epididymis - physiology; Epithelial Cells; Epithelium - chemistry; Epithelium - physiology; Fundamental and applied biological sciences. Psychology; Male; Mammalian male genital system; Membrane Potentials - physiology; Morphology. Physiology; Norepinephrine - pharmacology; Rats; Rats, Sprague-Dawley; Signal Transduction - physiology; Terpenes - pharmacology; Thapsigargin; Vertebrates: reproduction
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/BF00388302

A study was carried out to investigate the short-circuit current (Isc) response to noradrenaline (NA) and the signal transduction mechanisms involved in cultured rat cauda epididymal epithelium. In normal Krebs-Henseleit solution, NA (10 mumol.l-1) added basolaterally elicited a biphasic Isc response consisting of a transient spike followed by a second sustained response. The biphasic response was almost abolished by removing ambient Cl-. Preloading the tissues with a cell-permeant Ca2+ chelator, 1,2-bis(2-aminophenoxy) ethane-N,N,N',N',-tetraacetic acid acetoxymethyl ester (BAPTA/AM), or pretreating them with thapsigargin (Tg), a microsomal adenosine triphosphatase inhibitor abolished the initial spike in the Isc response to NA, but had little effect on the second component. Pretreating the tissues with a non-selective beta-antagonist, nadolol, reduced the second Isc response in a dose-dependent fashion but the initial spike was not affected. Microfluorimetric studies showed that NA (100 mumol.l-1) elicited single Ca2+ spikes in isolated epididymal cells, which could be abolished by prior treatment with Tg. Biochemical assays showed that NA (10 mumol.l-1) increased intracellular cyclic adenosine monophosphate concentration ([cAMP]i) and the response was abolished by prior treatment with nadolol (50 mumol.l-1). The results showed that NA elicited a biphasic Isc response mediated by a rise in intracellular Ca2+ concentration ([Ca2+]i) followed by a rise in [cAMP]i. The Ca(2+)-mediated Isc response had a faster onset and more transient action than the cAMP counterpart. It is suggested that NA released from noradrenergic nerve endings regulates transepithelial Cl- secretion in the epididymis thereby providing the specialized millieu vital for sperm storage and maturation.