Electrogenic active proton pump in Rana esculenta skin and its role in sodium ion transport.

摘要: Kinetic and electrophysiological studies were carried out in the vitro Rana esculenta skin, bathed dilute sodium solution, to characterize proton pump coupling between absorption (JNa+n) excretion (JH+n). JNa+n JH+n both dependent on transepithelial potential (psi ms); hyperpolarizing skin decreased increased JH+n; depolarization produced opposite effects. Amiloride (5 X 10(-5) M) at a clamped psi ms of +50 mV inhibited without affecting JH+n. Variations or pH had identical effects Ethoxzolamide simultaneously by 15-30 mV. These changes accompanied apical membrane mc from -47 -25 an increase resistance 30%; no significant basolateral cs) (Rb) nor shunt (Rj) observed. The appears be localized membrane. was also deoxygenation, oligomycin, dicyclohexylcarbodiimide vanadate (100, 78, 83 100% inhibition respectively). variations measured electrical currents significantly correlated. findings are supportive evidence primary active pump, electrogenic strictly linked aerobic metabolism. current-voltage (I-V) relation obtained as difference I-V curves extracted before after proton-pump ethoxzolamide during amiloride block transport. current (IP) best described saturable exponential function mc. Maximal (ImaxP) calculated 200 nequiv h-1 cm-2 reversal ERP -130 effect depolarize ERP. induced occurred whereas exerted minimal when approached either voltage clamping addition amiloride. We show that electroneutral sodium-proton countertransport is not mechanism frog but it which provides favourable driving force for passive entry.(ABSTRACT TRUNCATED AT 400 WORDS)