The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the uptake, distribution and excretion of a single oral dose of [11,12-3H]retinyl acetate and on the vitamin A status in the rat.

TCDD (2,3,7,8-Tetrachlorodibenzo-p-dioxin, 10 micrograms/kg body weight, p.o.) was given to male Sprague-Dawley rats 4 d before the oral administration of a physiological dose of [11,12-3H]retinyl acetate (RA). The rats were kept in metabolic cages for up to 192 h after RA administration. Radioactivity and/or vitamin A were determined in tissues and excreta. TCDD-pretreated and control rats excreted 41 and 23%, respectively, of the radioactivity of RA during the 192 h after administration. In control animals, 30% of the radioactivity of RA entered the liver within 6 h, the stores reaching 42% after 192 h. Maximum storage in TCDD-treated rats was 13% and after 192 h only 9% of the dose remained. A lag period of 12-24 h preceded the TCDD-induced increase in renal (175-671%) and serum (85-145%) radioactivity. In TCDD-treated rats less radioactivity was found in the intestine (45-79% decrease) and adrenals (14-73% decrease). Relative to the total body content, significantly more radioactivity was found in the kidney, serum, testes and epididymis of TCDD-treated rats. The decrease in vitamin A content after TCDD-treatment was 39-53% in the liver, 19-67% in the intestine and 18-44% in the epididymis. The kidneys of TCDD-treated rats contained more vitamin A (3-30 times more). TCDD treatment initially increased (42%) and later decreased (40%) the vitamin A content in the thymus as compared to controls. Pretreatment with a single low dose of TCDD thus affects both storage and excretion of radioactivity from newly administered RA as well as the vitamin A content in several tissues.