Transient glomerular hyperfiltration in the streptozotocin-diabetic Wistar Furth rat

The glomerular hemodynamic response to streptozotocin (STZ)-induced experimental diabetes differs depending on metabolic control and rat strain used. The present study characterize the glomerular filtration rate (GFR) and other renal parameters, weekly up to eight weeks of diabetes in STZ-diabetic Wistar Furth rats. The STZ-treated rats became diabetic within 24 h after treatment and retained a blood glucose concentration of 20-25 mmol/l throughout the experimental period. The GFR was transiently increased during the first 3-5 weeks after induction of diabetes, but thereafter did not differ from control animals. The renal weight increased by approximately 50% during the first week after induction of diabetes, thereafter no further increase in weight occurred. The urinary flow rate and urinary osmolar excretion were approximately 10 times higher in diabetic animals when compared to non-diabetic animals. Although they remained markedly higher than in non-diabetic animals, both the urinary flow rate and the urinary osmolar excretion peaked after 3 weeks of diabetes and thereafter tended to decrease. The urinary sodium and potassium excretions did not differ between non-diabetic and diabetic animals. We conclude that the transient increase in the GFR seen in the human disease, occurs in Wistar Furth rats, which is in contrast to a majority of other rat strains, where the GFR is persistently increased.