The effect of aging on the hepatic metabolism of sulfo-bromophthalein 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 (Tm) and relative storage capacity (S) were determined by a single infusion rate method by directly determining Tm from bile samples collected through a common bile duct cannula. Tm values expressed as micrograms of BSP per min per g of liver were highest in the youngest rate (3-month-old) as compared with the older rats (12-, 24-, 30-month-old) for all three rat groups. Tm 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 Tm period remained essentially unchanged with age in all three rat groups. S values, expressed as mg of BSP stored per mg or 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 Tm appears to decrease with age regardless of rat and sex, while S does not show such a decrease.