Albuminuria causes lysozymuria in rats with Heymann nephritis

To determine if changes in dietary protein intake alter renal excretion of small molecular weight proteins in passive Heymann nephritis, 21 rats with passive Heymann nephritis were fed 8.5% protein for 12 days after injection with antiserum. Dietary protein intake was then increased to 40% in 10 rats (LP-HP) while 11 rats remained on 8.5% protein (LP-LP). Lysozymuria (UlysV) increased from 66.5 +/- 31.0 mcg/day to 457.5 +/- 98.0 mcg/day (P less than 0.001) after five days in LP-HP, but was unchanged in LP-LP. Albuminuria (UalbV) increased only in LP-HP, from 168 +/- 23 mg/day to 447 +/- 45 mg/day (P less than 0.001). Urinary lysozyme excretion correlated with UalbV (r = 0.737, P less than 0.001), and changes in UlysV correlated with changes in UalbV (r = 0.657, P less than 0.01). To determine whether the increase in UlysV was the direct effect of the change in diet, enalapril 40 mg/kg/day was administered to prevent the increase in UalbV that occurs when these rats are fed a high protein diet. Twelve rats were fed 8.5% (LP) and 10 were fed 40% protein (HP) from the time of injection with antiserum. Six LP (LPE) and five HP (HPE) received enalapril. UlysV was 873 +/- 391 mcg/day in HP and nearly undetectable in the other three groups. UalbV was significantly greater in HP (368 +/- 60 mg/day) compared to the other three groups (114 +/- 16 in LP, 136 +/- 44 in HPE, 95 +/- 21 in LPE.(ABSTRACT TRUNCATED AT 250 WORDS)