On the Mechanisms of Sodium Ion Transport by the Irrigated Gills of Rainbow Trout (Salmo gairdneri)

摘要: Sodium uptake by rainbow trout gills has been investigated with a small-volume system enabling rapid, successive flux measurements in different solutions. influx obeys Michaelis-Menten type relation, Km of 0.46 mM, and proceeds unimpaired the absence penetrating counter-ions. This suggests coupled cation exchange. Ammonia output is about same as Na+ when external [Na+] 1 but at higher or lower influxes, correlation does not hold. A progressive downward shift pH irrigating medium increases indicates that exchanging hydrogen. In support this, acetazolamide, which inhibits uptake, also prevents shift. The potential across gill 10 mv, body fluids positive, NaCl solutions up to little affected changes concentration below that. Finally, evidence for locating rate-limiting step outer membrane epithelium presented.