Enrichment of periportal (PP) or perivenous (PV) hepatic zones by digitonin perfusion. Livers were first perfused in situ with hemoglobin- and albumin-free Krebs-Henseleit buffer via the portal vein as described in Materials and Methods.Uniform blood clearance was achieved with normal grade perfusion at a constant flow rate of 3.0 mL/min/g liver in a single-pass mode: (A) no digitonin treatment..