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KMID : 0358619910250010049
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Korean Journal of Physiology
1991 Volume.25 No. 1 p.49 ~ p.60
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Proton Transport in Human Placental Microvillous Membrane Vesicles
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Ri Ok-Kyung
Jung Jin-Sup
Kim Won-Whe
Lee Sang-Ho
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Abstract
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The change of the acridine orange absorbance was used to monitor the formation and/or dissipation of a pH gradient in microvillous membrane vesicles (MVV) isolated from human term placenta. Under efflux conditions, an acidification of the intravesicular space occured and it was completely inhibited by 0.1 mM amiloride. Under efflux conditions, an acidification of the intravesicular space occured and it was potentiated by valinomycin or FCCP. An inwardly directed chloride gradient also induced a minor intravesicular acidification, but it was not observed in voltage-clampled MVV. The initial rate of the dissipation of a pH gradient was accelerated by pulse injections of in a saturable manner and could replace . The kinetic parameter of in placental exchange was similar to that of renal exchange. Amiloride was a inhibitor of directly coupled exchange and its in placental MVV was about 14-fold higher than that in renal brush border membrane. These results indicate that exchanger exists in human placental MVV and that its kinetic characteristics is similar to that of renal exchanger but its pharmacological characteristics is different. In placental MVV , and, relatively minor chloride conductances are present. The magnitude of exchange, even though it exists, seems to be smaller than that of exchange.
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KEYWORD
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Proton transport, Microvillous membrane vesicles, Human placenta
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