Mechanisms of K+ uptake across the basal membrane of malpighian tubules of Formica polyctena: the effect of ions and inhibitors.

摘要: In the presence of 6 mmol l-1 Ba2+, known to block K+ channels in basal membrane, a rise bath [K+] ([K+]bl) induced an increase intracellular concentration ([K+]i) similar amount and time course that obtained absence Ba2+. The active passive (other than through channels) uptake mechanisms across membrane was investigated different concentrations. Dihydro-ouabain (10(-3) mol l-1), blocker Na+/K(+)-ATPase, tested low [K+], Sch28080 (10(-4) K+/H(+)-ATPase inhibitor, were without effect on fluid secretion. also electrical potential differences either or Vanadate contrast, strongly reduced secretion not only control solution but high-K+, Na(+)-free medium transepithelial apical difference [K+]i. Omitting Na+ from bathing medium, replacing Cl- by Br- applying bumetanide (10(-5) l-1) inhibited low-K+ (10 medium. 51 [K+]bl, omitting 10(-4) needed inhibit Replacing stimulated at this concentration. Bumetanide had no 113 [K+]bl. [K+]bl did affect potentials, lower [K+]i observed results summarized model proposing play dominant role high-K+ (113 A K+/Cl- cotransporter may become more important K+/Na+/2Cl- gain importance 10 Active for seem detectable sustaining response vanadate might be due electrogenic H+ pump.