Increase of phosphotyrosine levels in mouse urine and liver during liver regeneration after partial hepatectomy.

To determine how cell proliferation contributes to phosphotyrosine (P-Tyr) level in body we investigated the changes of P-Tyr levels in mouse urine and liver during liver regeneration after partial hepatectomy (PH). After PH, the P-Tyr contents in urine and liver increased approximately 14- and 1.7-fold, respectively, at 2-4 days, and P-Tyr phosphatase activity in liver decreased to 50% at 2 days. These levels returned to the control level at 10 days. After orthovanadate administration, P-Tyr level increased as P-Tyr phosphatase activity decreased. These results suggest that P-Tyr level in liver is reflected in urinary P-Tyr level during liver regeneration, and P-Tyr phosphatase is important in the regulation of P-Tyr level.