ELEVATED LEVELS OF TRIMETHYLAMINE OXIDE IN MUSCLES OF DEEP-SEA GADIFORM TELEOSTS - A HIGH-PRESSURE ADAPTATION

Trimethylamine oxide (TMAO) as an osmolyte typically occurs at 20-70 m M in shallow-water marine teleost fishes. However, it has not been pre viously examined in deep-living species. We collected species from two families of benthic gadiform teleosts by otter trawl from the contine ntal slope (1,800-2,000 m) and abyssal plain (2,850 m) off the Oregon coast. Muscle and plasma samples were analyzed for TMAO with a picric acid method. Muscle contents (below in millimoles/kilogram of wet weig ht) were found to be higher than previously reported for teleosts. Res ults from Macrouridae from 1,800-2,200 m were as follows: Albatrossia pectoralis, 83 +/- 10; Coryphaenoides cinerus, 121 +/- 11. Results fro m Macrouridae from 2,850 m were significantly higher: C. leptolepis, 1 58 +/- 20; C. fillifer, 177 +/- 8; C. armatus, 173 +/- 5. Caught at bo th depths, Antimora microlepis (Moridae) had 211 +/- 14. Plasmas had l ow TMAO (2-15 mM) and high Na+ concentrations (227-273 mM), except A. microlepis plasma, which had the lowest Na+ (219 +/- 30 mM) and highes t TMAO (159 +/- 46 mM). Osmotic pressures of fresh plasma (423-557 mos m) correlated highly with muscle TMAO and with plasma TMAO plus Na+ le vels. These higher osmolalities may reduce osmoregulatory costs. Howev er, as a methylamine known to stabilize protein, TMAO may counteract d estabilizing effects of hydrostatic pressure on cellular proteins. Wit h purified C. leptolepis muscle lactate dehydrogenase, 250 mM TMAO ful ly offset a 30% increase in NADH Km induced by 300 atm. (C) 1997 Wiley -Liss, Inc.