STEREOLOGICAL ESTIMATES OF VOLUME-WEIGHTED MEAN GLOMERULAR VOLUME IN STREPTOZOTOCIN-DIABETIC RATS

BACKGROUND: The stereological estimate of mean glomerular volume is an objective and reproducible method of measuring glomerular size in terms of absolute volume. This method provides objective, unbiased, and reproducible data that may be used in the description of glomeruli. EXPERIMENTAL DESIGN: We have made a morphometric analysis of glomerular size in three cortical areas (superficial, midcortical, and juxtamedullary) in normal and diabetic animals, using the point-sampled intercepts method. The kidney weight and volume as well as the cortical and glomerular volume density were also calculated. Our study included 35 animals (5 control and 30 experimental). Fifteen experimental animals were treated with 50 mg/kg streptozotocin dissolved in citrate buffer at pH 4.5. The other 15 animals were sham injected with citrate buffer. In all cases the tissues were fixed in 10% formaldehyde and embedded in paraffin. Sections were cut at 4 mum and stained with periodic acid-Schiff and a systematic sampling was performed. RESULTS: In the control and experimental groups the juxtamedullary glomeruli were significantly larger than superficial and midcortical glomeruli. Mean values of the kidney weight and volume and the volume-weighted mean glomerular volume show a significant increase at 4, 20, and 50 days after streptozotocin-induced diabetes. CONCLUSIONS: The increase in the volume-weighted mean glomerular volume was similar in the three cortical areas, thus suggesting that the effect of diabetes on glomerular enlargement is similar in all cortical areas.