Abstract
Ketoconazole, an imidazole derivative, has been implicated in a number of hepatic dysfunctions. The aim of the present study was to determine the effect of in vivo treatment of rats with ketoconazole on individual serum bile acid levels and the in vitro effects of ketoconazole on the hepatocellular uptake of two bile acids and two other model substrates transported by liver cells. Male Sprague-Dawley rats were treated i.p. with a single injection of ketoconazole of 25 mg/kg (n = 4) or 50 mg/kg (n = 4); the control group (n = 4) received the vehicle only at a dose of 1 ml/kg. Blood samples were collected at 4 hr after dosing. With high-performance liquid chromatography, the serum was assayed for individual serum bile acids. At the higher dose, ketoconazole produced a significant increase in serum levels of cholic acid, taurocholic acid, chenodeoxycholic acid, glycocholic acid, glycochenodeoxycholic acid, glycodeoxycholic acid, deoxycholic acid and taurochenodeoxycholic acid compared with the control group (P < .05). Cholic acid, taurocholic acid and chenodeoxycholic acid levels were significantly raised in rats treated with the lower dose. In vitro, ketoconazole strongly inhibited the hepatocellular uptake of [14C]cholic acid, [14C]taurocholic acid and [3H]ouabain but not [14C]2-aminoisobutyric acid, which indicated that the effect is relatively specific. The kinetics of inhibition were competitive and the inhibition constants for taurocholate and ouabain were 6 and 1 microM, respectively. Ketoconazole inhibited by both Na(+)-dependent taurocholate uptake and stimulated bile acid countertransport of preloaded hepatocytes.