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Journal of Experimental Biology 121,251-270 (1986)
Published by Company of Biologists 1986

Epithelial Amino Acid Transport in Marine Mussels: Role in Net Exchange of Taurine between Gills and Sea Water

STEPHEN H. WRIGHT 1 and TIMOTHY W. SECOMB 1

1 Department of Physiology, College of Medicine, University of Arizona, Tucson AZ 85724, USA

The exchange of taurine across epidermal epithelia of Mytilus edulis and M. californianus was studied U9ing radiotracer and chromatographic (HPLC) methods. Gill levels of taurine in both species ranged from 60 to 70µmolg-1 wet weight. Net uptake of taurine, determined using HPLC, occurred down to ambient concentrations as low as 10 nmol-1. The rate of taurine loss from mussels was about 0.02/µmolg-1 wet body weighth-1, and when exposed to amino-acid-free sea water, external taurine concentration increased until a steady-state of about 15 nmoll-1 was achieved. Mussels accumulated inhibitors of taurine transport at rates which were directly related to their relative inhibitory capacities: {beta}-alanine >{beta}-aminobutyric acid {gamma}-aminobutyric acid (GABA). Addition of large concentrations (50-200 µmol-1) of GABA resulted in a rapid increase in taurine concentration in test solutions. This increase was consistent with a model in which GABA both competitively inhibits the reaccumulation of endogenous taurine lost from epidermal tissues, and accelerates the exchange diffusion of taurine from surface cells. We suggest that epidermal taurine transport in Mytilus assists in the maintenance of large intracellular taurine concentrations, and can serve to reaccumulate up to 30 % of the taurine lost from surface tissues by passive processes.

Key words: amino acid transport, Mytilus, gills, epithelia

Accepted on October 21, 1985






© The Company of Biologists Ltd 1986