lab20 - J. Physiol.(1972),222,pp. 549-509 497 With4...

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Unformatted text preview: J. Physiol.(1972),222,pp. 549-509 497 With4 text-figures PrintedinGreatBritain CHANGES IN THE INTESTINAL TRANSPORT OF SODIUM INDUCED BY EXPOSURE OF GOLDFISH TO A SALINE ENVIRONMENT BY J.C. ELLORY, B.LAHLOU* AND M. W. SMITH From the A.R.C. Institute of Animal Physiology, Babraham, Cambridge (Received 17 December 1971) SUMMARY 1. The uptake andtransfluxofsodium bygoldfish intestines hasbeen compared underdifferent experimental conditions. Uptake was measured from a 1min contact ofthe intestinal mucosa with radioactivesodium chloridesolution.Transfluxwas measuredovera period of2hr using the evertedsac technique. 2. Keepinggoldfish insalinereduced the transflux ofsodium to one quarter thevaluefound forfresh-waterfish.The uptake ofsodium was halved by thistreatment. Cortisol injectedpreviously into saline-adapted fish changed neither the transflux nor the uptake ofsodium measured subsequently. 3. In fresh-waterfish hypophysectomy reducedsodiumtransfluxwhile leaving the uptake ofsodium unchanged.Injection ofcortisolrestored sodium transflux to control levels without producing any additional effectson the uptake ofsodium. 4. It is suggested that adaptation tosalineinvolves regulation ofsodium movement across themicrovillarmembrane ofthemucosal cell.Cortisol would appear to play no part in this type of regulation. 5. The presence of cortisol, or possibly other steroids with similar actions, hashoweverbeenshowntobeessentialforthenormal operation ofsodium transport in this tissue. It isnot clear exactly how cortisol exerts thiseffect.What evidence thereis suggests that cortisolexertsa metabolic control rather than changing directly the membrane per- meability ofthecell. * Member of the C.E.A. Groupe de Biologie Marine, Villefranche-sur-Mer. Presentaddress:Laboratoirede PhysiologieComparee, Facult, desSciencesde Nice, France. ) by guest on March 23, 2010 Downloaded from J Physiol ( 498 J.C. ELLORY, B.LAHLOU AND M. W. SMITH INTRODUCTION The ability of euryhaline fishtoincreasetheirintestinal absorption of sodium and water on entering a hypertonic saline environment iswell known.Thefunctionofthis adaptive response seemsto lie primarily inthe maintenance ofan adequate water balance, theextra sodium being ex- creted by the gills so thatthe plasma sodiumremains essentiallyunchanged by theincreaseinexternal salinity. The goldfish, which isa fresh-water fish, can also adapt toa salineenvironmentbutthis adaptation differsin some respects from thatfound forthe trulyeuryhaline fish.The initial response ofthe goldfishgill to increased salinity, likethat of gills from euryhaline fish, is to excrete sodium, but in the case of goldfish this adaptiveresponse cannot fully compensate for the increased influx of sodium which takes place immediately fish are placed in saline. The plasma concentrationofsodium approaches or slightly exceedsthatofthe externalmedium and theflowofurinedecreases (Lahlou, Henderson & Sawyer, 1969)....
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This note was uploaded on 09/12/2010 for the course BIOLOGY 225 taught by Professor Pavgi during the Winter '10 term at University of Michigan.

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lab20 - J. Physiol.(1972),222,pp. 549-509 497 With4...

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