Effects of C-peptide on the single-nephron glomerular filtration rate in early diabetic rats

Objective: Single-nephron glomerular filtration rate (SNGFR) is an important and valuable parameter for evaluating renal function. Previously, SNGFR measure-ments required radioactive labelling of isolated animal nephrons, which was a time-consuming and inefficient process. Owing to the development of laser confocal microscopy, in vivo renal visualisation became much simpler, facilitated by the use of fluorescent markers. In this study, the effects of C-peptide on hyperfiltration reversal were evaluated during the early stages of diabetes mellitus (DM). Methods: Wistar rats (n = 17) were divided into control and streptozotocin-induced DM groups. Analyses were performed at 2 and 6 weeks following induction. Lucifer Yellow was administered by bolus injection to visualise tubular urinary flow using a laser confocal microscope. Results: SNGFR increased in diabetic rats ( p < 0.05) and decreased by approximately 40% following C-peptide administration ( p < 0.05). Moreover, tubular luminal flow increased ( p < 0.05), as previously reported, but decreased by 3–11% after C-peptide administration in 6-week diabetic rats without significance. Conclusion: Confocal microscopy demonstrated that C-peptide administration decreases SNGFR and tubular luminal flow in diabetic rats.