AJP - Cell Physiology, Vol 248, Issue 3 241-C246, Copyright © 1985 by American Physiological Society
Hydrogen transport in papillary collecting duct of rabbit kidney
A. Prigent, M. Bichara and M. Paillard
To examine the cellular mechanisms of H+ transfer in rabbit papillary
collecting duct (PCD), the 5,5-[14C]dimethyloxazolidine-2,4-dione-derived
cell pH (pHi), the [3H]triphenylmethylphosphonium-derived membrane
potential (Em), the lumen-to-cell Na+ concentration gradient [(
Na+]o/[Na+]i), and cell potassium and chloride concentrations were studied
at 37 degrees C in separated PCD from rabbits pretreated with
deoxycorticosterone acetate. The variations in cell pH values were used as
an index of changes in H+ secretion. Under standard conditions pHi was 7.30
+/- 0.04, [Na+]o/[Na+]i was 2.46 +/- 0.43, Em was 78 +/- 7 mV (cell
negative), [K+]i was 105 +/- 10 mM, and [Cl-]i was 33 +/- 6 mM; the value
of pHi thus remained higher than expected if H+ ions were passively
distributed (6.13). Acetazolamide, 10(-4) M, alkalinized the cells. When
[Na+]o/[Na+]i was reduced (low-Na+ medium or 10(-3) M ouabain), the cells
did not acidify, suggesting that net H+ secretion did not decrease; also,
pHi was not linked to the variations in the transmembrane chloride
concentration gradients. When the cells were depolarized (low-Na+ medium),
they became more alkaline; when the cells were hyperpolarized (10(-4) M
amiloride), they became more acid; minor change in Em (ouabain) was
associated with no change in pHi. It is concluded that: 1) H+ is actively
secreted into the lumen; 2) active H+ secretion may not be secondary, via
electroneutral Na+:H+ countertransport or HCl cotransport, but probably
occurs via a primary H+ pump; 3) variations in Em probably affect pHi by
acting on both the active H+ transport system and passive movements of
HCO-3 (or its equivalent).
