Increased Glomerular Hydrostatic Pressure is Associated with Tubular Creatinine Reabsorption in Healthy Subjects

Abstract

Background: Cr is secreted by the proximal tubules and thus Cr clearance (C_cr) can overestimate inulin clearance (C_in). However, in some cases, C_cr can even underestimate C_in. This suggests that Cr could be reabsorbed in the tubuli. We examined the clinical parameters that are associated with tubular Cr reabsorption. Methods: In 80 kidney donor candidates (53.9 ± 13.2 years, 29 males), C_in and para-aminohippuric acid clearance were measured simultaneously. Intrarenal hemodynamic parameters were calculated by Gomez’s formulae. To quantify the secretory component of C_cr (SF_cr), it was calculated as follows: SF_cr = (C_cr − C_in)/C_cr. Results: Twenty-five subjects (31.3%) showed SF_cr values <0. SF_cr that correlated significantly and negatively with efferent arteriolar resistance (R_e) and glomerular hydrostatic pressure (P_glo) (R_e: r = −0.30, p = 0.008; P_glo: r = −0.28, p = 0.025). In multiple regression analyses, R_e and P_glo were significantly and negatively associated with SF_cr after adjustment for other confounders. Conclusions: These findings suggest that tubular reabsorption of Cr can occur in some cases. Intrarenal glomerular hemodynamic burden may be related to tubular creatinine reabsorption, which possibly leads to lower C_cr values.