INS and diabetes mellitus: Creatinine clearance may be considered an imperfect method for measuring the glomerular filtration rate (GFR) but, because this study employed the same methodology in all animals, the higher creatinine clearance values in diabetic compared to nondiabetic rats after 8 weeks of diabetes are viewed as corresponding with the hyperfiltration of early onset and long duration that has been observed in this model of insulin deficient diabetes (O'Donnell et al. 1988; Stackhouse et al. 1990), which may not be accompanied by a significant change in plasma creatinine (Benigni et al. 2003).