Studies on the toxicity and metabolism of β-apo-8′-carotenal in dogs

Abstract

Dogs tolerated daily administration of 1000 mg and 100mg of β-apo-8′-carotenal for 14 weeks without the occurrence of toxic manifestations; general health, blood counts, liver and kidney function tests remained within normal limits. In terms of vitamin A activity, these doses are equivalent to 1,166,900 IU and 116,690 IU. Gross and microscopic findings were not unusual except for some deposition of yellow pigment in mesenteric and perirenal adipose tissue of dogs treated with 1000 mg of apocarotenal; on occasion, some pigment was also found in the renal cortex, adrenals, and liver of these animals. Plasma vitamin A levels were not elevated despite the prolonged treatment interval; levels of apocarotenal in plasma were significantly increased in dogs given 1000 mg of this carotenoid. Assays of the tissues showed the kidneys of treated animals to contain three- to fivefold higher amounts of vitamin A than controls; apocarotenal concentrations also tended to be elevated in dogs administered this carotenoid orally. Metabolites found in the urine of dogs repeatedly administered this carotenoid include, in addition to β-apo-8′-carotenal, free and esterified vitamin A and β-8′-apocarotenoic acid.