Comparison of hilar and capsular renal lymph

The sites of origin of renal lymph were studied by analysis of simultaneously collected samples of lymph and plasma. The samples included renal hilar (HL) and capsular lymph (CL), thoracic duct lymph (TD), renal venous (RVP) and arterial plasma (AP), and were analyzed for Na+, Cl-, K+, urea, glucose, inulin, and PAH concentrations. The glucose concentrations of HL (76 mg/100 ml, SE +/- 1.9), and CL (92 mg/100 ml, SE +/- 2.5) were significantly different (P less than 0.01) from that of RVP (86 mg/100 ml, SE +/- 2.2). Concentrations of both inulin and PAH in CL and HL fell between the AP and RVP values. The concentration of inulin in CL (CL/RVP = 1.27) exceeded that in HL (HL/RVP = 1.10), but no such difference was detected for PAH. The Na+ (152 meq/liter) and Cl- (129 meq/liter) concentrations in HL were significantly (P less than 0.01) higher than those in CL (Na+ = 148 meq/liter; Cl- = 120 meq/liter), in TD (Na+ = 146 meq/liter; Cl- = 121 meq/liter), and in RVP (Na+ = 144 meq/liter; Cl- = 114 meq/liter. These differences remained highly significant when the electrolyte concentrations were converted to milliequivalents per kilogram H2O. In contrast, no significant differences were detected between the concentrations of urea in the various fluids sampled. It is concluded that CL and HL do not drain a perfectly homogeneous intrarenal pool, and that they do not equilibrate with RVP or AP within the kidney. The results also indicate that CL and HL derive a small component from tubular reabsorbate; that for CL stemming from the cortex, and that for HL from the deeper cortex and outer medulla.