The effect of aging on the hepatic metabolism of sulfobromophthalein in BN/Bi female and WAG/Rij male and female rats

The effect of aging on sulfobromophthalein (BSP) metabolism was studied in three groups of rats—BN/Bi female and WAG/Rij male and female rats—of different ages ranging from 3 to 30 months. Under Nembutal anesthesia, BSP biliary transport maximum (T_m) and relative storage capacity (S) were determined by a single infusion rate method by directly determining T_m from bile samples collected through a common bile duct cannula. T_m values expressed as μg of BSP per min per g of liver were highest in the youngest rats (3-month-old) as compared with the older rats (12-, 24-, 30-month-old) for all three rat groups. T_m gradually decreased as age increased and at the age of 24 or 30 months reached a value of 66–70% of the highest values for 3-month-old rats. The percentage of conjugated BSP in the bile measured during the T_m period remained essentially unchanged with age in all three rat groups. S values, expressed as mg of BSP stored per mg of BSP per ml of plasma per g of liver, remained unchanged (BN/Bi female) or even increased (WAG/Rij male and female) with age. As a consequence, S values expressed per rat were higher in older age groups than in the youngest one for all three rat groups. In contrast with previous reports by other authors on man and rats, the BSP T_m appears to decraese with age regardless of rat strain and sex, while S does not show such a decrease.