Mechanism and regulation of proton transport in the outer medullary collecting duct.
Our understanding of transport and its regulation in the OMCDi has expanded significantly over the past 5 years. The OMCDi cells of the rabbit appear to be ideal for studying the mechanism and regulation of proton transport in a cell which is functionally similar to the alpha intercalated cell of the cortical collecting tubule. Characterization of the specific transporters at the apical and basolateral membrane allows us to explore further the mechanism whereby hormones and their second messengers regulate net transport in these cells. Simultaneous electrophysiologic measurements and determination of intracellular ion activities with fluorescent dyes, a technique we are currently employing in studies of single alpha and beta intercalated cells of the cortical collecting tubule, will be required to make progress in our study of regulation. Finally, characterization of the transporters has demonstrated that these cells are more complex than initially thought. Especially exciting is the possibility that the apical membrane proton extrusion step may be accomplished by more than one mechanism, i.e., a proton ATPase or an H(+)-K(+)-ATPase.
Jacobson
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Vanderbilt University Medical Center, Division of Nephrology, Nashville, Tennessee.
Furuya
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Breyer
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D000818:Animals; D001692:Biological Transport; D000242:Cyclic AMP / Q000502:physiology; D007679:Kidney Medulla; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism*; D011522:Protons
D011522:Protons; D000242:Cyclic AMP