Abstract
Ca uptake rates and efflux rate coefficients were determined in isolated renal tubules of the winter flounder, Pseudopleuronectes americanus. Na-free medium and 10(-4) M ouabain depressed while 0.2 mM dinitrophenol stimulated Ca efflux. The effects on Ca movement appeared to be associated with the adenosine triphosphate (ATP) concentration of the tubular fluid space (TFS), rather than the bath-to-tissue Na gradient. Elevation of the ATP concentration of TFS by incubation of tissue in external ATP more than doubled Ca uptake rate. Inhibition of Ca uptake by lanthanum and stimulation by Ca ionophore A23187 suggested that ATP altered plasma membrane Ca transport. Incubation in external phosphate had no effect. Plasma membrane vesicles (PMV) prepared from flounder tubules showed saturable Ca uptake inhibited by Mg, unaffected by Na gradients, and stimulated by intravesicular but not extravesicular ATP. ATP appeared to stimulate PMV Ca uptake by increasing membrane Ca binding. We concluded that Ca uptake across the peritubular membranes was not directly linked to the serosal Na gradient but was greatly influenced by the intracellular ATP concentration.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
