Renal elimination of protein S-100β in pigs with acute encephalopathy

Background: Protein S-100β is an established biochemical marker for cerebral injury in serum. For the further interpretation and possible use of S-100β serum measurements in acute hepatic encephalopathy, renal elimination of S-100β was measured in pigs with elevated S-100β levels due to hepatic encephalopathy. Methods: Eighteen female Norwegian Landrace pigs were randomly allocated to either hepatic devascularization (n = 13) or sham operation (n = 5). Repeated samples from the common carotid artery, right renal vein, and urine were simultaneously drawn for S-100β analysis, using the Sangtec100 Liamat immunoassay. Results: In hepatic devascularized pigs, arterial serum levels of S-100β increased from 0.96 ± 0.04 μg/L (mean ± SEM) at t = 0 h to 1.74 ± 0.11 μg/L (mean ± SEM) at t = 5h. Urinary excretion increased simultaneously from 8.48 ± 3.66ng/h (mean ± SEM) to 20.4 ± 9.54 ng/h (mean ± SEM), while renal arterial-venous fluxes for both kidneys increased from 1022 ± 404 ng/h (mean ± SEM) to 2444 ± 590 ng/h (mean ± SEM). Conclusions: Increased arterial S-100β levels in pigs with acute hepatic encephalopathy are not a result of decreased renal elimination. The large difference between the renal arterial-venous S-100β concentrations and the urinary excretion of S-100β indicate that renal metabolism is the major route of elimination.