Control of ion transport by the sperm duct epithelium of brook trout (Salvelinus fontinalis) |
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Authors: | William S Marshall Sharon E Bryson David R Idler |
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Institution: | (1) Department of Biology, St. Francis Xavier University, Antigonish, NS;(2) Marine Sciences Research Laboratory, Memorial University of Newfoundland, St. John's, NF, Canada;(3) Department of Biology, St. Francis Xavier University, Antigonish, Nova Scotia, Canada, B2G 1C0 |
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Abstract: | The sperm duct epithelium of brook trout (Salvelinus fontinalis), mountedin vitro in Ussing-style epithelial chambers actively absorbs Na+ (measured as the short-circuit current, Isc) and secretes K+ (measured using86Rb+ as tracer). Dibutyryl-cyclic-adenosine monophosphate (db-cAMP) and 3-isobutyl-1-methylxanthine (IMX) produce a rapid, sustained
stimulation of both ion transport processes, but the hormone connected to the response is unknown. Purified sockeye salmon
CON A2 gonadotropin (GtH) produces a dose-dependent, rapid and sustained rise in Na+ uptake and K+ secretion. The time course, electrophysiological and transport characteristics are similar to those evoked by IMX. Carbohydrate-poor
(chum salmon CON A1) GtH is ineffective. Pretreatment of fish with 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) significantly
increases milt volume but is without effect on resting or stimulated (IMX + db-cAMP) levels of sperm duct ion transport. This
is the first indication of a direct, rapid action of GtH on ion transport by the vertebrate blood-testis barrier. The results
suggest direct involvement of GtH in control of later stages of sperm maturation. |
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Keywords: | teleost salmonid reproduction gonadotropin seminal plasma potassium secretion 17α 20β -dihydroxy-4-pregnen-3-one |
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