Absence of focal glomerulosclerosis in aging analbuminemic rats

The Nagase analbuminemic rat (NAR), a mutant of the Sprague-Dawley (SD) strain, exhibits high levels of plasma cholesterol (Chol), thrombocytosis, and enhanced platelet aggregability, which might promote glomerulosclerosis (GS). To determine whether NAR are more susceptible than SD rats to aging GS, young (3-mo-old) and aging (18-mo-old) SD rats and NAR were studied. In young NAR, glomerular pressure and glomerular volume were lower, whereas total and high-density lipoprotein plasma Chol levels were higher than in young SD rats. Aging SD rats developed glomerular hypertension and hypertrophy. Less glomerular enlargement and subnormal glomerular pressures were seen in aging NAR. Enhanced platelet aggregation developed in aging SD rats, approaching the values seen in NAR. Similarly elevated levels of low-density lipoprotein Chol were seen in additional SD rats and NAR studied at 12 mo of age. Plasma triglyceride (TG) levels were lower in NAR at this age. Only SD rats developed proteinuria and exhibited GS and glomerular lipid deposits at 18 mo of age. Reduced glomerular wall stress due to lower glomerular pressure and volume as well as lower TG levels may explain the absence of GS in aging NAR despite plasma lipid and platelet abnormalities.