title: Determination of unidirectional fluxes of phosphate across plasma membrane in isolated perfused rat liver.
abstract: In livers labeled with 32P by intraperitoneal injection 18 h before perfusion the unidirectional efflux of inorganic phosphate (Pi) was a linear function of the concentration of Pi in the intracellular exchangeable pool of Pi (range, 0--1 mumol/g liver). Calculations of the efflux were based on determination of the specific radioactivity of Pi in the intracellular exchangeable pool of Pi by a new method. Zero efflux was found at biopsy concentrations of Pi of about 1.8 mumol/g liver. The influx of Pi was calculated from the efflux and the net uptake of Pi; it was found to be related to the extracellular concentration of Pi in a fashion that was approximately linear. An increase in the concentration of Pi in the input medium gave rise to an increased influx and, with a time delay, also to a gradually increasing efflux. The increased efflux could be explained as a consequence of an increased intracellular concentration of exchangeable Pi.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D008099:Liver / Q000378:metabolism* / Q000502:physiology; D008564:Membrane Potentials; D010477:Perfusion; D010710:Phosphates / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats
chemical_list: D010710:Phosphates