Antiporter in Xenopus Laevis Oocytes
نویسندگان
چکیده
The amiloride-sensitive Na + /H + antiporter in defolliculated oocytes of Xenopus laevis was characterized by measurements of H Na + influx and apparent H + efflux. Uptake of ^Na"" was linear over a 90-min incubation period and was inhibited approximately 80% with 5xlO~moll~ amiloride. Amiloride-sensitive sodium uptake was reduced following collagenase treatment or oocyte aging. Ko 5 for amiloride inhibition was 4.13xl0"±1.33xl0"moll" and the Km for Na + was 4.25xlO~moll~. Hill analysis of the kinetic data for Na revealed an nH value of 1.14, indicating an absence of interacting binding sites for Na. Parallel measurements of amiloride-sensitive Na uptake and H + efflux indicated a Na + /H + exchange ratio of 0.88:1. Our conclusion is that the Na + /H + antiporter of Xenopus oocytes exhibits a nominal 1:1 N a + / H + exchange stoichiometry and is similar in its properties to the antiporter of other vertebrate cells.
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