PROTON TRANSPORT AND CHLORIDE CELLS IN THE GILL OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Particulate preparations from freshwater rainbow trout (Oncorhynchus m ykiss) gill homogenates contain an active magnesium ion activated ATPa se that transports protons into the-vesicles. Oligomycin at a concentr ation of 20 mug.mL-1 had little effect on the proton transport, which was completely inhibited by N-ethylmaleimide. This inhibition was part ly counteracted by dithiothreitol. Proton transport in freshwater trou t gill submitochondrial particles was completely inhibited by oligomyc in. When freshwater trout were kept for 40 min in water equilibrated w ith air containing 5% carbon dioxide, their gill lamellar epithelium c ontained many cells densely covered with erect microvilli. After chang ing to water bubbled with room air, the cells rapidly lost their micro villi. Control fish that were killed immediately after removal from th e storage tank also had microvilli, but less erect and fewer in number . Labelled latex microspheres and dextran were used as markers for ext ernal medium uptake into gill epithelial cells. The fish were pretreat ed by bubbling the water by air containing 5% carbon dioxide, and the uptake took place when the water was bubbled with room air.