title: Some factors affecting phosphate transport in a perfused rat heart preparation.
abstract: Pi uptake by a perfused rat heart preparation did not require the presence of any other permeant anion, but was markedly dependent on the extracellular Na+ concentration and accelerated when tissue oxygenation was inadequate. Pi efflux was also independent of other permeant anions, but apparently varied with the intracellular Na+ concentration. Cardiac Pi efflux was not sensitive to a number of inhibitors that clock Cl- movement in heart and other tissues. Both uptake and efflux apparently proceed via a reversible electroneutral co-transport system linked to the transmembrane Na+ gradient. Pi uptake was independent of cardiac work load, but the efflux rate was sharply accelerated after an increase in aortic pressure development, with a slow return towards basal values during sustained periods of high work output. An inverted biphasic effect on the efflux rate was observed after a reduction in cardiac work load. Mild hypoxia and respiratory and metabolic acidosis each resulted in a transient acceleration of Pi efflux followed by a return towards basal values during prolonged exposure to the stimulus, whereas respiratory and metabolic alkalosis produced a similar but inverted response. The origin of these phasic effects on Pi efflux remains to be identified at present.
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005665:Furosemide / Q000494:pharmacology; D006321:Heart / Q000187:drug effects; D000860:Hypoxia / Q000378:metabolism; D066298:In Vitro Techniques; D007477:Ions / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009599:Nitroprusside / Q000494:pharmacology; D010477:Perfusion; D010710:Phosphates / Q000378:metabolism*; D005082:Physical Exertion; D051381:Rats
chemical_list: D007477:Ions; D010710:Phosphates; D009599:Nitroprusside; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D005665:Furosemide