QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by AHEARN, G. A. Articles by TOWNSLEY, S. J. Search for Related Content PubMed Articles by AHEARN, G. A. Articles by TOWNSLEY, S. J.

Journal of Experimental Biology 62,733-752 (1975)
Published by Company of Biologists 1975

Integumentary Amino Acid Transport and Metabolism in the Apodous Sea Cucumber, Chiridota Rigida

GREGORY A. AHEARN ¹ and SIDNEY J. TOWNSLEY ²

¹ Hawaii Institute of Marine Biology, University of Hawaii, P.O. Box 1346, Kaneohe, Hawaii 96744
² Department of Zoology, University of Hawaii, Honolulu, Hawaii 96822

1. The apodous sea cucumber, Chiridota rigida, was found to transport exogenous amino acids to intracellular free amino acid pools in the integument, the gastrointestinal epithelium making only a minimal contribution to total animal uptake.

2. Amino acids entering the integumentary free amino acid pool were either completely catabolized to CO₂, incorporated into large molecular weight compounds, such as proteins, or left unchanged. The latter fraction was available for efflux through both apical and basal cellular membranes through saturable or non-saturable transport processes.

3. Influx of natural (glycine) and analog (AIB) amino acids into the integumentary epithelium was achieved by a combination of saturable and non-saturable transport mechanisms: the former displaying Michaelis- Menten kinetics, being Na⁺-dependent, and transporting both glycine and AIB; the latter involving a simple diffusion of amino acid across the apical cell membranes and/or through the intercellular septate desmosomes.

4. Preloaded AIB exhibited both homo- and hetero-exchange diffusion with exogenous amino acids when a relatively large internal analog pool had been established. With a small internal pool of AIB, homo-exchange diffusion persisted, but high external concentrations of glycine inhibited the washout of the analog.

5. Transintegumentary influx of AIB to the coelomic fluid was a linear function of the exogenous amino acid concentration and was unchanged when choline chloride was used as a substitute saline. At steady-state the coelomic fluid analog concentration was maintained at a much lower level than the incubation medium or the epithelial free amino acid pool, due to apparent absorptive processes of the dermis and muscle layers of the integument, as well as by possible carrier-mediated re-uptake mechanisms on the basal membranes of the epithelial cells.

6. A tentative model of integumentary amino acid transport and metabolism in C. rigida is presented.