| 12507602 |
Agalakova NI, Gusev GP: Effect of protein kinase C activation on Na+-H+ exchange in erythrocytes of frog Rana temporaria. Comp Biochem Physiol A Mol Integr Physiol. 2003 Jan;134(1):11-20.
The treatment of frog erythrocytes incubated in standard nitrate medium with 100 nM phorbol ester (PMA) induced a sharp increase in the 22Na uptake by the cells and intracellular Na (+) concentration. The PMA-induced enhancement in 22Na uptake was stimulated by the addition of 0.1 mM ouabain to the incubation medium and completely blocked by 1 mM amiloride. The time course of 22Na uptake by frog red cells in the presence of PMA showed a lag phase ( approximately 5 min), after which was linear within 5-15 min. The calculated Na (+) influx in erythrocytes treated with PMA was 49.4+/-3.7 mmol l (-1) cells h (-1) as compared with 1.2+/-0.25 mmol l (-1) h (-1) for control cells. 5-(N-ethyl-N-isopropyl)-amiloride, selective blocker of NHE1, caused a dose-dependent inhibition of the PMA-induced Na (+) influx with IC (50) of 0.27 microM. The PMA-induced Na (+) influx was almost completely inhibited by 0.1 microM staurosporine, protein kinase C blocker. Pretreatment of frog red blood cells for 5, 10 or 15 min with 10 mM NaF, non-selective inhibitor of protein phosphatase, led to a progressive stimulation of the PMA effect on Na (+) influx. Both amiloride and NaF did not affect the basal Na (+) influx in frog erythrocytes. The data indicate that the Na (+)-H (+) exchanger in the frog erythrocytes is quiescent under basal conditions and can be markedly stimulated by PMA. |
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