Localization of tissue sodium and potassium compartments in rabbit renal cortex

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Abstract
It had been concluded on the basis of previous studies of isotope exchange in kidney slices and tubule suspensions that multiple Na and K compartments exist in renal tissue. In the present studies the anatomical localization of these compartments has been determined. The exchange of Na22 and K42 was measured in each of the individual cortical segments of the rabbit nephron in vitro. The exchange rates for K42 differed in the various segments examined, being most rapid in the thick ascending limb and slowest in the proximal tubule and collecting tubule. It is concluded that the multiple K compartments found in whole renal tissue reflect different pools in the separate segments of the nephron. In contrast Na22 exchanged in the proximal nephron, at least, at 2 different rates, indicating multiple intracellular compartments rather than cellular heterogeneity.