Inhibition of renal accumulation of lysozyme (basic low molecular weight protein) by basic proteins and other basic substances

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Abstract
Together the two rat kidneys accumulated a total of 31.7±1.6% of the intravenously injected amount of 7 nmoles egg-white-lysozyme (measured as iodine 125-lysozyme) within 10 min. The low molecular weight protein lysozyme and other basic substances were injected simultaneously in order to evaluate whether these basic substances can inhibit the tenal lysozyme accumulation. The inhibitory effect of various basic compounds was dose-dependent with a maximal reduction of lysozyme accumulation to 11.7±0.8%. The basic substances could be divided into three groups depending upon the micromolar amount injected at which a 50% inhibition was achieved (0.3–1.2 μmoles: cytochrome C, ribonuclease; 10.9 μmoles: spermine; 501–688 μmoles:l-arginine,l-lysine). The neutral myoglobin had no effect on renal lysozyme accumulation. The inhibitory potency appeared to increase with increasing molecular weight and pI value of the substances tested. Microperfusion experiments of proximal convoluted tubules of rat kidney revealed that luminal reabsorption of the basie lysozyme can be inhibited by the basic protein cytochrome C in a dose-dependent fashion. In these experiments the perfusion solution contained 57 μmol·l−1 lysozyme, an intratubular lysozyme concentration at which the tubular lysozyme reabsorption was found to be about 80% saturated. A 50% inhibition of the tubular endocytic lysozyme reabsorption was achieved at a cytochrome C concentration of 102 μmol·l−1.