EFFECT OF OVARIECTOMY ON GLOMERULAR INJURY IN HYPERCHOLESTEROLEMIC FEMALE IMAI RATS

To clarify the pathogenesis of focal and segmental glomerulosclerosis, we investigated the effect of ovariectomy in hypercholesterolemic fem ale Imai rats. At 5 weeks of age, control female (group 1) and control male rats (group 3) were sham-operated, female rats (group 2) were ov ariectomized and male rats (group 4) were castrated. Body weight, bloo d pressure, urinary protein and serum constituents were checked every 2 months from 2 through 12 months of age. All groups were studied morp hologically at 6 months of age and further female groups (1 and 2) stu died at 12 months. Both control female and control male rats developed marked proteinuria, to a significantly greater extent in the male rat s. Castration reduced proteinuria, while ovariectomy did not influence it and there were no significant differences in proteinuria among the control females, the ovariectomized females and the castrated males. Control male rats had significantly lower serum albumin levels, higher cholesterol levels and a significantly greater impairment of renal fu nction in blood urea nitrogen (BUN) levels than did the control female rats at 6 months. Castration significantly increased serum albumin le vels and lowered BUN levels, while ovariectomy did not basically influ ence these values in the female rats. The glomerulosclerosis index at 6 months of age was significantly higher in the control males than in the control females. Castration attenuated glomerular injury, while ov ariectomy aggravated glomerular injury to the same levels as found in the castrated males. This aggravating effect of ovariectomy observed a t 6 months, however, disappeared at 12 months. These results suggested that sex-related factors regulated by the ovaries may play an inhibit ory role in the development of glomenulosclerosis before 6 months of a ge, but not thereafter, in hypercholesterolemic female Imai rats.