Effects of hydrostatic pressure on gill Na-K-ATPase in an abyssal and a surfacing-dwelling teleost

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1. 1. A comparison of gill Na-K-ATPases isolated from the surface dwelling sea water adapted coho salmon, Oncorhynchus kisutch , and a benthic marine teleost, Antimora rostrata , was initiated to study the effects of hydrostatic pressure on gill ion flux. 2. 2. Specific activities of the two enzymes are similar, as are the effects of high hydrostatic pressure which results in large + ΔV ‡ values (enzyme inhibition). However, at physiological pressures, activation is seen in the Antimora enzyme. This observation, plus ouabain sensitivity and enzyme stability, suggest these two enzymes have distinctive catalytic properties. 3. 3. Due to an inability to prepare a stable Na-K-ATPase preparation from Antimora gills, affinity parameters could not be determined. However, the significant alteration in these parameters with high pressure, especially the K m(Na + ) , seen for the coho enzyme suggest that substantial changes in Na + efflux could occur which would be detrimental in an abyssal habitat. 4. 4. It has been postulated that Antimora rostrata gills lack chloride cells, and that an alternative extrarenal salt secretory mechanism may be utilized. This may account for the results reported in this paper.