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Urea transport across the cell membrane of skate erythrocytes

✍ Scribed by Carlson, Sarah R.; Goldstein, Leon

Publisher: John Wiley and Sons
Year: 1997
Tongue: English
Weight: 103 KB
Volume: 277
Category: Article
ISSN: 0022-104X
DOI: 10.1002/(sici)1097-010x(19970301)277:4<275::aid-jez1>3.0.co;2-m

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✦ Synopsis

The aim of this study was to determine the mechanism of urea transport by the erythrocyte cell membrane of the little skate, Raja erinacea. Radioisotope tracer studies demonstrated that urea transport is bi-directional and is not saturable. Experiments using urea homologues and analogue indicated that urea transport was not subject to competitive inhibition. Phloretin and p-chloromercuric phenylsulfonic acid (pCMBS), two inhibitors of facilitated diffusion, did not block urea transport. All these studies support the hypothesis that urea traverses the membrane via simple diffusion. Therefore, we determined whether urea enters the cell through a channel/pore or through the lipid bilayer. Studies were done using a series of urea derivatives of different molecular size and lipid solubility. Two techniques which determined hemolysis time and extent of hemolysis indicated that despite differences in size, the limiting factor in the transport of urea (and its homologues and analogues) is lipid solubility. These studies suggest that urea is transported by simple diffusion through the lipid phase in the skate erythrocyte membrane.

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