Active transport of water, sodium, potassium and α-oxoglutarate by kidney-cortex slices

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Abstract
Slices of guinea pig kidney cortex lost 40% of their initial K content to, and gained an extra 60% Na from, a saline medium during the 1st 5 min. of aerobic incubation at 37[degree] and pH 7.4. These changes were reversed after 30 min. with 10 mM alpha-oxoglutarate as substrate. During aerobic incubation at 37[degree] for 40 min. the sum of Na and K contents of the tissue rose by 25.7[plus or minus]3.2[mu] moles per g. tissue, while the content of dibasic alpha-oxoglutarate rose by the equivalent amt. of 12.0 [plus or minus]0.6 [mu] moles per g. tissue. The sum of Na and K concns. in the tissue water was 1.29 times greater than that in the medium; the alpha-oxoglutarate concn. was 2.6 times greater. During this time 53.3[plus or minus]5.5[mu] moles alpha-oxoglutarate per g. tissue were metabolized. All concn. gradients of Na, K and alpha-oxoglutarate between slices and medium were reduced or disappeared during aerobic or anaerobic incubation at 0[degree], or anaerobic incubation at 37[degree]. The dry wt. of the tissue decreased during incubation by 9.0% at 37[degree] in O2 and by from 22 to 26% at 37[degree] in N2 or at 0[degree] in either O2 or N2. During incubation of tissue in a hypotonic medium at 0[degree], the water content increased and the sum of Na and K contents fell concomitantly. Movements of Na and K separately continued after the movement of water was complete. These results confirm that in guinea pig kidney-cortex slices the prevention of swelling, and the production and maintenance of Na and K concn. gradients are dependent upon a supply of energy from respiration.