[The role of GTP-binding proteins in regulating the activation of Na+/H+-exchange and Na+, K+, 2Cl- cotransport: effect of fluoride ion].

The effects of NaF and AlCl3 on basal and stimulated by hyperosmotic shock activities of Na+/H(+)-exchange and Na+, K+, 2Cl(-)-cotransport in rat smooth muscle and red blood cells have been studied. Preincubation of cells with 10 mM NaF leads to inhibition of basal and hyperosmotic shock-activated Na+, K+, 2Cl(-)-cotransport in smooth muscle cells--by 45% and 190%, respectively. Sodium fluoride causes 80% activation of basal Na+, K+, 2Cl(-)-cotransport in red blood cells with no effect on the transport induced by hyperosmotic shock. The effect of NaF on Na+, K+, 2Cl(-)-cotransport in red blood cells does not depend on Al3+. Basal Na+/H(+)-exchange is stimulated by NaF by 780% in smooth muscle cells and is insensitive to the fluoride in red blood cells. Under hyperosmotic conditions NaF activates Na+/H(+)-exchange by 100% in smooth muscle cells and by 130% in red blood cells; in the latter case its effect is potentiated by Al3+. The data obtained suggest that GTP-binding proteins are involved in the activation of Na+/H(+)-exchange under hyperosmotic conditions.