Renal function and morphology in aged Beagle dogs before and after hydrocortisone administration

Objectives of this study were to evaluate glomerular filtration rate (GFR), renal structural changes and proteinuria in aged Beagle dogs before and after administration of hydrocortisone. Eleven Beagle dogs 65 10 years were treated with either hydrocortisone (HC group, n=6) or a placebo (control group, n=5). Measurement of urinary markers, GFR and kidney biopsies were performed before (T0), during (T16wks) and after discontinuing HC administration (T24wks). Results indicate that HC administration causes a significant increase in GFR. During HC treatment, proteinuria, urinary albumin-to-creatinine (c) ratio, immunoglobulin G/c and retinol-binding protein/c were higher compared to baseline in the HC group. At T0, rare to mild glomerular, tubular and interstitial lesions were detected in all HC dogs and rare to moderate changes in all control dogs. Glomerulosclerosis progressed in both groups, with most severe scores at T24wks. Tubular atrophy was detected in 3 HC dogs at T16wks and T24wks, but was also found in up to 5 control dogs throughout the study. At every time point, up to 5 HC dogs and all control dogs had rare to moderate interstitial inflammation. Rare to mild interstitial fibrosis was found in up to 3 HC dogs at T16wks and T24wks, and severe fibrosis in 1 HC dog at T24wks. Up to 4 control dogs had rare to mild fibrosis at all time points. These findings indicate that clinically healthy, aged Beagle dogs may have considerable renal lesions and proteinuria, which could have implications for experimental or toxicological studies. Additional research is needed to further elucidate glucocorticoid effects on renal structure, but functional changes such as hyperfiltration and proteinuria warrant attention to kidney function canine patients with Cushing's syndrome or receiving exogenous glucocorticoids