AJP - Renal Physiology, Vol 253, Issue 2 282-F289, Copyright © 1987 by American Physiological Society
Control of steady-state pH in rabbit proximal straight tubules
J. L. Atkins and M. B. Burg
Steady-state pH (defined as the limiting pH reached at slow flow rates) was
measured in isolated perfused rabbit proximal straight tubules (S2). With
normal bath conditions (pH 7.4, bicarbonate 25 mM) the luminal steady-state
pH was 6.85. Steady-state pH was directly related to bath pH and
bicarbonate, but not to bath PCO2. Lowering of bath pH or bicarbonate
consistently decreased luminal steady-state pH, and raising either caused
steady-state pH to increase. When bath PCO2 was increased, on the other
hand, steady-state pH either increased or decreased, depending on the
concomitant changes in bicarbonate and pH. The changes in steady-state pH
observed in the present studies following alterations in bath pH and
bicarbonate concentration should, when extrapolated to the in vivo kidney,
result in decreased delivery of bicarbonate from the proximal tubule in
acidosis and increased delivery in alkalosis. The effects of potassium and
chloride were also determined. Removal of potassium from the bath increased
the steady-state pH, but removal of chloride from both the perfusate and
bath had no significant effect.
