Assessment of the longevity of the liver using a rat transplant model.

To assess the longevity of the liver, arterialized, orthotopic liver grafts were performed using syngeneic male BN/BiRij rats. Young (5-month-old) livers were transplanted into 5-month-old recipients (group I, n = 27), and old (28-month-old) livers were transplanted into 5-month-old rats (group II, n = 28). Recipient survival after transplantation was similar in both groups. The average age of the livers at the time of death was 16.7 months in group I and 39.1 months in group II. Four of the livers in group II survived for more than 4 years (48.1 to 52.4 months). Early deaths (less than 1 year) after transplantation were most commonly caused by biliary obstruction and cholangitis in both groups. Late deaths (more than 1 year) after grafting were mainly from heart failure or tumors. None of the animals died of liver failure or liver disease. Weight gain in the rats, total serum protein levels, and alanine transaminase levels after transplantation did not differ significantly between the two groups. There was a trend for the histological features of aging of the liver-fibrosis, bile duct proliferation, and pigment deposition-to become more prevalent as the livers became very old (mean age, 46 months). Nevertheless, typical aging changes, as individual findings, were absent in nearly half of the oldest organs. The alterations in morphology had no apparent effect on the ability of the livers to sustain the lives of the recipients. The liver of the BN/BiRij rat was capable of surviving far beyond the maximum life span of BN/BiRij rats, and rats in general. It did not become diseased in the process.