Initial Rate Of Na Research Articles

Insulin-mediated Na+ transport in the toad urinary bladder

The characteristics of insulin-induced Na+ transport in the toad urinary bladder were determined and compared to those of aldosterone. Bladders were mounted in modified Ussing chambers, and standard short-circuit current techniques were employed to measure transepithelial Na+ transport. Insulin added to the serosal medium is much more effective than insulin added to the mucosal medium. Serosal insulin concentrations from 10(1) to 10(3) muU/ml increase both the initial rate and the final level of Na+ transport achieved, whereas concentrations from 10(3) to 10(5) muU/ml increase only the initial rate of Na+ transport. Insulin-induced Na+ transport probably does not require glucose. Both insulin- and aldosterone-induced Na+ transport are directly proportional to serosal (but not mucosal) K+ concentration over the physiologic range (2.0-7.0 meq/liter). However, cycloheximide abolishes aldosterone- but not insulin-induced Na+ transport. In addition, insulin stimulates Na+ transport after a maximal response to aldosterone, and aldosterone stimulates Na+ transport after a maximal response to insulin. Thus, although they have several similar characteristics, insulin and aldosterone have at least partially independent mechanisms of action on Na+ transport in the toad urinary bladder.

Light-induced glutamate transport in Halobacterium halobium envelope vesicles. I. Kinetics of the light-dependent and the sodium-gradient-dependent uptake.

During illumination Halobacterium halobium cell envelope vesicles accumulate [3H]glutamate by an apparently unidirectional transport system. The driving force for the active transport originates from the light-dependent translocation of protons by bacteriorhodopsin and is due to a transmembrane electrical potential rather than a pH difference. Transport of glutamate against high concentration gradients is also achieved in the dark, with high outside/inside Na+ gradients. Transport in both cases proceeds with similar kinetics and shows a requirement for Na+ on the outside and for K+ on the inside of the vesicles. The unidirectional nature of glutamate transport seems to be due to the low permeability of the membranes to the anionic glutamate, and to the differential cation requirement of the carrier on the two sides of the membrane for substrate translocation. Thus, glutamate gradients can be collapsed in the dark either by lowering the intravesicle pH (with nigericin, or carbonyl cyanide p-trifluoromethoxyphenylhydrazone plus valinomycin), or by reversing the cation balance across the membranes, i.e., providing NaCl on the inside and KCl on the outside of the vesicles. In contrast to the case of light-dependent glutamate transport, the initial rates of Na+-gradient-dependent transport are not depressed when an opposing diffusion potential is introduced by adding the membrane-permeant cation, triphenylmethylphosphonium bromide. Therefore, it appears that, although the electrical potential must be the primary source of energy for the light-dependent transport, the translocation step itself is electrically neutral.

Effect of antidiuretic hormone on sodium uptake across outer surface of frog skin.

ARTICLESEffect of antidiuretic hormone on sodium uptake across outer surface of frog skinTU Biber, and LJ CruzTU Biber, and LJ CruzPublished Online:01 Oct 1973https://doi.org/10.1152/ajplegacy.1973.225.4.912MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByRegulation of apical Na+ conductive transport in epithelia by pHBiochimica et Biophysica Acta (BBA) - Reviews on Biomembranes, Vol. 1241, No. 1NaCl Transport in Amphibian SkinThe role of sodium-channel density in the natriferic response of the toad urinary bladder to an antidiuretic hormoneThe Journal of Membrane Biology, Vol. 64, No. 1-2Effect of Li and of other ions on Na transport in epithelial cells of frog skinBiochemical Pharmacology, Vol. 29, No. 16Effect of external cation and anion substitutions on sodium transport in isolated frog skinThe Journal of Membrane Biology, Vol. 52, No. 2Effect of FeCl3 on ion transport in isolated frog skinThe Journal of Membrane Biology, Vol. 52, No. 2Colchicine inhibition of ADH effect on frog skin permeabilityExperientia, Vol. 34, No. 3Transport Across Amphibian SkinTransport Across Amphibian Urinary BladderIonic exchanges in isolated and open-circuited toad skinThe Journal of Membrane Biology, Vol. 35, No. 1Sodium pump stimulation by oxytocin and cyclic AMP in the isolated epithelium of the frog skinPflügers Archiv European Journal of Physiology, Vol. 371, No. 3Computer modelling. Application to studies on the initial rate of Na+ uptake by frog skin epidermisJournal of Theoretical Biology, Vol. 65, No. 4Effects of insulin on short-circuit current and Na-K-ATPase activity of the toad skin and urinary bladderComparative Biochemistry and Physiology Part A: Physiology, Vol. 58, No. 2Na-K-ATPase and transepithelial sodium transport in the toadComparative Biochemistry and Physiology Part A: Physiology, Vol. 56, No. 4Effects of Cd++ on short-circuit current across epithelial membranesThe Journal of Membrane Biology, Vol. 26, No. 1Solute transport across isolated epitheliaKidney International, Vol. 9, No. 2Structure and Function of the EpidermisLithium transport across isolated frog skin epitheliumThe Journal of Membrane Biology, Vol. 25, No. 1Effects of furosemide on sodium content and transport pool in frog skin (Rana esculenta)Naunyn-Schmiedeberg's Archives of Pharmacology, Vol. 290, No. 2-3 More from this issue > Volume 225Issue 4October 1973Pages 912-917 Copyright & PermissionsCopyright © 1973 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1973.225.4.912PubMed4542709History Published online 1 October 1973 Published in print 1 October 1973 Metrics

IRREVERSIBLE EQUILIBRATION OF BARLEY ROOTS WITH NA+IONS AT DIFFERENT EXTERNAL NA+CONCENTRATIONS

SUMMARY Roots of decapitated barley plants were allowed to equlibrate with Na+ solutions of different concentration. The kinetic characteristics of this process were examined. Attainment of the saturation level appeared to involve not only strong reduction of the net flux but also of the influx as measured with 22Na+. The final Na+ content of the tissue depended on the external Na+ concentration. Reckoned from a certain level of internal Na+ the relationship was the same as for the initial rate of Na+ uptake. Transfer of roots saturated at a low Na+ concentration to a more concentrated Na+ solution brought about a resumption of Na+ absorption until a level characteristic of the new concentration had been attained. On the other hand transfer of the material from a higher to a lower concentration after saturation did not involve appreciable loss of Na+ from the tissue. A kinetic model is proposed to explain these phenomena.