Castration attenuates proteinuria and glomerular injury in hyperlipidemic male Imai rats

Hyperlipidemic Imai rats spontaneously develop proteinuria and glomerulosclerosis, especially in males. We investigated the effect of castration on spontaneous proteinuria and progressive renal injury in male Imai ats. Male Imai rats (n = 16) were castrated at 5 weeks of age. Body weight, blood pressure, urinary protein excretion and serum constituents were checked and compared with sham-operated control rats (n = 16) up to 24 weeks. Sham-operated group 1 (n = 5) and castrated group 2 (n = 6) underwent morphological study after 16 weeks of observation and sham-operated group 3 (n = 11) and castrated group 4 (n = 10) were followed for an additional 8 weeks and used for morphological study. Growth rate was significantly stunted in castrated rats as compared with the controls. Castration significantly reduced proteinuria almost throughout the experiment (167 +/- 84 vs. 46 +/- 24 mg/kg/day, p < 0.001, at 8 weeks and 688 +/- 211 vs. 458 +/- 97, p < 0.01, at 20 weeks). The glomerulosclerosis index was significantly higher in sham-operated control rats than in castrated rats (28.8 +/- 18.0 vs. 7.3 +/- 3.1, p < 0.01, at 16 weeks, and 92.1 +/- 35.5 vs. 39.5 +/- 8.9, p < 0.001, at 24 weeks). There were no significant differences in blood pressure, serum cholesterol, plasma renin activity, plasma somatomedin C levels between the two groups. These results raise the possibility that sex hormones may partly contribute to spontaneous proteinuria and progressive renal injury in male Imai rats.