Abstract
Summary
Phosphorus uptake and oxygen consumption by particles from rat liver, with a-ketoglutarate as substrate, are almost completely inhibited by 0.0007 N Ca++ and completely inhibited by 0.0014 N Ca++; this effect may be a specific one upon phosphorus uptake or transfer, as the oxygen uptake with pyruvate and hexose diphosphate as substrate is not markedly impaired at the same Ca++ concentrations. Citrate used in concentrations equivalent to the calcium had no protective effect against the Ca++ inhibition, but larger ratios of citrate to calcium afforded partial or complete protection. Attempts to obtain oxidative phosphorylation with washed particles obtained from Walker 256 rat tumor homogenates, using a-ketoglutarate as substrate, were unsuccessful. Wide variations in concentration of magnesium appeared to exert no effect on the phosphorus uptake and oxygen consumption of washed rat liver particles.
When homogenates, particles, and supernates of rat liver, rat brain, and the Walker rat tumor 256 were subjected to the action of calcium with hexose diphosphate and pyruvate as substrate, the maximal inhibiting effect on the phosphorus uptake of homogenates and particles was noted with liver, an intermediate effect was obtained with brain, and a minimal effect was found with tumor. In all cases the phosphorus uptake, lactate production, and oxygen uptake of supernates were unaffected by calcium chloride at concentrations up to 0.0028 N.
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