Study of quality in fish and shellfish as food. IV. Levels of oxolinic acid in cultured yellowtail after oral administration.

Levels of an antibacterial agent, oxolinic acid, in yellowtail after oral administration were determined by high performance liquid chromatography, and the following results were obtained. 1) The recoveries of oxolinic acid from muscle, liver, kidney and blood were 86, 78, 84 and 77%, respectively. 2) After oral administration of oxolinic acid, dosage of 200mg/kg, the concentration of the drug in the tissues reached peak levels of 1.2-4.9 μg/ml or g at 3-9h post dosing, followed by a gradual decrease to ‹1μg/ml or g within 24h post dosing. High concentration of oxolinic acid was observed in the order of kidney› bile› spleen› muscle› blood› brain› liver. 3) After oral administration of oxolinic acid, dosage of 50mg/kg, the drug disappeared almost entirely from the blood and the liver at 3-day post dosing, while the remaining drug was detected in muscle, kidney, spleen and brain at 8-day post dosing. 4) Glucuronic acid conjugate of oxolinic acid was found in all the tissues by treatment with β-glucuronidase. The unidentified compound was also found in tissues, especially liver and bile at 3 and 24-h post dosing (200mg/kg), it conjugated with glucuronic acid and had no antibacterial activity against Aeromous sp.