In response to osmotic swelling and shrinkage respectively, the Amphiuma erythrocyte exhibits volume induced K/H and Na/H exchange. Coincident with the increases in dissipative fluxes there is also a 5-fold stimulation of the Na/K ATPase (see also Siebens and Kregenow,1985). In contrast to the case of volume induction where the alkali-metal proton exchangers are coordinated around the volume set point, exposure of Amphiuma red blood cells in isotonic media to the protein phosphatase inhibitor Calyculin-A (luM) causes simultaneous induction of both Na/H and K/H exchangers. The Calyculin-induced fluxes are 83 fold (Na/H) and 663 fold (K/H) as great as those observed in isosmotic media. As is the case with volume perturbation, Calyculin also stimulates Na/K ATPase activity, operationally defined as ouabain inhibitable "Rb uptake. In this regard, the Calyculin-induced Na/K ATPase activity is some 34 fold greater than that in isosmotic media. The Calyculin-induced increase in the Na/K ATPase activity is not due to an increase in [Na], since [Na], increased from 12 to 18.9 mM (during the flux period). In contrast, if cells are allowed to maximally load with Na during volume regulation in hyperosmotic media for 130 min., [Najj increases from 18 to 123 mM, yet the Na/K ATPase activity is only about 18% of that in Calyculin treated cells. In conclusion, it appears that Calyculin A is able to induce increased Na/K ATPase activity, independent of changes in [Na];. Supported by HL21179-16 to P.M. Cala and an NIH minority supplement to Alejandro Ortiz-Acevedo.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology