Induction of a dose-related increase in sulfobromophthalein uptake velocity in freshly isolated rat hepatocytes by phenobarbital
✍ Scribed by Barry J. Potter; Jia-Zhang Ni; Kathleen Wolfe; Decherd Stump; Paul D. Berk
- Publisher
- John Wiley and Sons
- Year
- 1994
- Tongue
- English
- Weight
- 760 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0270-9139
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✦ Synopsis
To determine whether phenobarbital affects hepatocellular bilirubinlsulfobromophthalein uptake mechanism, we administered it to male Sprague-Dawley rats, body weight 175 f 25 g m , at doses of 1 to 75 mg/kg body wtiday for 7 days. Control rats were given an equivalent volume of physiological saline solution. On day 8, hepatocytes were isolated by means of collagenase perfusion, suspended in Hanks' solution without albumin and incubated with high specific activity (3 Ciimmol) [ 3"SJsulfobromopht halein, which was synthesized in our laboratory and purified by means of a new reverse-phase high-pressure liquid chromatography procedure. The initial uptake rate of sulfobromophthalein was determined at sulfobromophthalein concentrations of 1 to 50 pmolL with a rapid filtration technique. The maximum uptake velocity and Michaelis constant for sulfobromophthalein uptake at each phenobarbital dose were determined by means of a computer analysis. In control studies, maximum uptake and Michaelis constant were 48.0 rf: 16.7 (mean rf: S.D.) pmoli50,OOO cells/min and 22 f 4 pmolL, respectively. Maximum uptake velocity increased linearly with the log of the phenobarbital dose (r = 0.98, p i 0.01), the increase achieving statistical significance at a dose of 3 mg/kg/day. Michaelis constant, however, was essentially unchanged at phenobarbital doses of 50 mg/kg/day or less. The maximal observed increase in maximum uptake velocity of sulfobromophthalein (to 619% of control values) was appreciably greater than the maximal increase in UDP-glucuronyltransferase activity (200% of control)