SECRETION OF NITROGEN INTO THE SWIMBLADDER OF FISH. II. MOLECULAR MECHANISM. SECRETION OF NOBLE GASES

¹ The Marine Biological Laboratory, Woods Hole, Massachusetts 02543
² The Marine Biological Laboratory, Woods Hole, Massachusetts 02543, and The Department of Physiology, Albert Einstein College of Medicine, Bronx, New York 10461
³ The Department of Physiology, Division of Graduate Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104

Toadfish (Opsanus tau) were maintained at 50 m depth, 6 atm total pressure. The partial pressures of argon and nitrogen in the gases brought into the experimentally emptied swimbladder exceed the ambient pressures. The fraction of nitrogen in the gases brought into the swimbladder is nearly independent of depth. This finding is inconsistent with an earlier hypothesis that active oxygen secretion, by forming minute bubbles, drives nitrogen secretion. Toadfish were maintained in seawater equilibrated with mixtures containing oxygen, nitrogen, helium (in previous experiments), neon, argon, krypton and xenon. The more soluble gases are enriched in the mixture brought into the swimbladder, so that the composition of the inert gases brought into the swimbladder is similar to the composition of the gases dissolved in blood plasma. The enhancements, ([Gas/N₂]_secreted÷[Gas/ N₂]_ambient), of the gases in the mixture brought into the swimbladder are proportional to the solubility of the gases in water. These facts support the hypothesis that salting out of inert gases elevates the partial pressure of nitrogen and other inert gases in the gas gland blood vessels. High gas pressures may be generated by counter-current multiplication of this initial effect.