Studies on the hydrolysis in vitro of phthalate esters by hepatic and intestinal mucosal preparations from various species.

Esters of phthalic acid are extensively used as industrial solvents and plasticizers in the manufacture of a wide variety of plastics, including food-packaging materials. When administered orally to the rat, the metabolites in urine of a number of phthalate diesters appear as derivatives of the corresponding monoesters (Albro et al. 1973; Albro & Moore, 1974). Further, the most commonly used phthalate ester plasticizer, namely di42-ethylhexyl) phthalate (Autian, 1973), is metabolized in vitro by a number of rat tissues to mono-(Z-ethylhexyl) phthalate and 2-ethylhexanol (Albro & Thomas, 1973; Carter et al. 1974). In view of the widespread use of these compounds, we have studied the metabolism in vitro of a series of phthalate esters by both hepatic and small intestinal mucosal preparations obtained from the rat, ferret and the olive baboon. 14C-labelled dimethyl, diethyl, di-n-butyl, di-n-octyl, di-(2-ethylhexyl) and dicyclohexyl phthalates were prepared from [~arbonyl-~"C]phthalic anhydride by the method of Albro et al. (1973). Whole liver homogenates (0.25g/ml) were prepared in 0.25 M-sucrose and post-mitochondria1 supernatant fractions obtained by centrifugation at loo00 gav. for 20min. Intestinal-niucosal cells were scraped from the first 30-40cm of small intestine and homogenized in 0.25~-sucrose. The rates of hydrolysis of the