Fd Chem. Toxic. Vol. 31, No. 1, pp. 37-40, 1993 0278-6915/93$6.00 + 0.00 Printed in Great Britain.All fights reserved Copyright © 1993Pergamon Press Ltd RATES OF UTILIZATION OF INTRAVENOUS OLEYLANILIDE ADMINISTERED CHRONICALLY TO THE RAT A. RODRiGUEZ-MARTiN, X. REMESAR and M. ALEMANY* Departament de Bioquimica i Fisiologia, Universitat de Barcelona, 08028 Barcelona, Spain (Accepted 18 September 1992) Abstract--The constant injection of [14C]oleylanilide into the vena cava of Wistar rats for 7 days with osmotic minipumps was used to estimate tissue distribution of chronically administered anilides. The largest concentrations of the anilide were found in the brown adipose tissue; all other tissues showed much lower proportions. When anilide distribution was expressed as nmol/g lipid, the high concentration of the compound in the brown adipose tissue contrasted with its very low presence in the white adipose tissue; all other tissues showed intermediate concentrations. Anilide-treated rats consumed more food and lost more weight than did controls; their energy balance showed higher energy inefficiency. The results suggest a possible effect of anilides on the thermogenic pathway of the rat brown adipose tissue. In addition, there was a large individual variability in the proportions of anilide present in all tissues, from as little as 0.3% of the total anilide injected in some animals to 6% in others. INTRODUCTION The toxic oil syndrome, which affected a large number of people in Spain in 1981, has been related to the contamination of rapeseed oil with aniline (Pestafia and Mufioz, 1982). The presence of fatty acid-aniline (anilide) has been demonstrated in oil samples (Fournier et al., 1982; Tabuenca, 1981; Ventura-Diaz, 1982). Despite numerous studies, the administration of anilides in the diet did not significantly affect the health of most laboratory animals (Altman and Grunow, 1983). The rat detoxifies rapidly the ingested oleylanilide, eliminat- ing most of the aniline residue soon after through urine (Altman and Grunow, 1983). Chronic adminis- tration of anilides in the diet did not produce any apparent ill effects in rats, nor did acute injection of these compounds (Altman and Grunow, 1983; Casals et al., 1983; Maestro-DurUm et al., 1986). It has long been suspected that the rat intestine is able to split anilides into their aniline and fatty acid moieties (Irons et al., 1980), using the fatty acids in lipid metabolism and detoxifying the aniline (Smirez et al., 1985). In the present study, tissue distribution of chroni- cally administered anilides was investigated by constant injection of [14C]oleylanilide into the vena cava of rats for 7 days. A series of experiments was designed to circumvent the intestinal barrier since it is both a suspected site for hydrolysis of anilide-amide bonds and the first filter that *To whom correspondence should be addressed at: Depar- tament de Bioquimica i Fisiologia, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain. allows only an indeterminable portion of the anilide and its degradation products to pass into the blood- stream. MATERIALSAND METHODS Treatment of animals. Female Wistar rats weighing 200-220 g were used. The animals were kept under standard conditions (temperature 22-23°C, 12-hr light/dark cycle and humidity 65-75%) and were fed a pelleted chow (type A04; Panlab, Barcelona, Spain) and tap water. Six rats randomly selected were anaes- thetized with sodium pentobarbital (ip), and a mini- osmotic pump (Alzet, type 2001; Alza Research, Palo Alto, CA, USA) was inserted in the mesenteric cavity after limited laparotomy. The minipump released its content into the lower vena cava through capillary tubing (PE-50, i.d. 0.58 mm; Clay-Adams, Beckton- Dickinson & Co., Parsippany, NJ, USA) maintained in place with a drop of cyanoacrylate glue. The miniosmotic pumps were filled with a solution of oleylanilide in Tween 80 (500 g/litre or 560/~mol in 0.5 ml) containing 180 kBq/mol of uniformly labelled [t4C]oleylanilide. The pumps released the anilide mix- ture at a rate of 0.002 ml/hr (i.e. 0.906 nmol/s); over 7 days 553/~mol oleylanilide was released into the rat bloodstream (measured by weighing the amount of anilide solution at implantation time and that re- maining after 7 days). A control group (six rats) was implanted with minipumps filled with only Tween 80. Both groups were weighed daily and their food consumption was recorded. The energy equivalence of the food pellets used was 14.6 kJ/g. The energy equivalence of body weight losses was assumed to be uniform for each unit of body weight lost, with a mean equivalence of 10.75 kJ/g (Rothwell and Stock, 37