Relations between metabolism and the rate of turnover of sodium and potassium in guinea pig kidney-cortex slices

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Abstract
The uptake of radioactive Na by aerobic guinea pig kidney-cortex slices in a steady-state at 37[degree] can be represented by the empirical function. P=76[-l-exp (-2.65t), 24[-l-exp(-0.151t)], where P is the percentage exchange, and t is the time in minutes. Anaerobically at 37[degree] the function is P=55[l-exp (-4.45t)] + 45[l-exp(-0.134t)], and at 0[degree], aerobically and anaerobically, P=34[l-exp(-8.28t)] + 66[l-exp (-0.0954t)]. This means that Na exchanged as at least 2 fractions and that both the relative amts. and the turnover-rates of the fast and slow fractions of tissue Na changed with temp. and rate of respiration. The rapidly exchanging tissue Na apparently occupied an "outer" space of about 50% of the tissue volume at 37[degree] and 25% at 0[degree]. All the tissue intracellular K exchanged uniformly at 37[degree]both aerobically and anaerobically with rate constants of 0.206 and 0.145 min -1, respectively. In contrast, the uptake of radioactive K at 0[degree] in a steady-state can be represented by P= 37 [l-exp(-0.228t)] + 63[l-exp(-0.00194t)l, and anaerobically at 0[degree] by the function, P= 37 [l-exp(-0.160t)l + 63[l-exp(-0.00069t)]. This means that at 0[degree] the intracellular K exchanged as at least 2 fractions. Respiration increased the turnover-rates (%/min.) of Na and K at 37[degree] by only 34 and 42%. Thus, about 75% of the aerobic turnover-rates are independent of respiration. The turnover-rates in O2 were not affected by absence of substrate or the presence of 2,4-dinitrophenol despite major changes in the respiration rate and the amount of cations present.

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