COLLECTING DUCT HYDROGEN-ION SECRETION IN RABBIT - ROLE OF POTASSIUM

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 91  (6) , 948-959
Abstract
The distal nephron H+ secretion in the intact rabbits was studied. The rabbit was studied because it produces acid urine containing little ammonium. Replacing the usual rabbit diet with milk, plus administration of an acid load (10 meq/kg), the urine pH fell consistently from very alkaline values (pH > 7.4) to 4.8 .+-. 0.2. Despite the ability to achieve high urine-to-blood H+ concentration gradients, the U-B PCO2 [urine-blood CO2 partial pressure gradient], an index of collecting duct H+ secretion, was virtually zero. In these studies, the urine HCO3 and buffer concentration were comparable to those observed in dog, rat and man in which a high U-B PCO2 gradient was achieved. The rabbits studied had low plasma K concentrations (< 3 meq/L). Since K deficiency has been implicated in impaired urine acidification, K was administered and it resulted in an increase in collecting duct H+ secretion as evidenced by a further fall in minimum urine pH during acidemia and a prompt rise in the U-B PCO2 during alkali administration. Rabbits had a very low, but not absent, rate of collecting duct H+ secretion. K administration increased the rate of H+ secretion in a segment of the collecting duct in which H+ secretion is reflected by an increase in U-B PCO2.

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