A significant rise in plasma triacylglycerols from the control level of 0.89 mmol/l to 1.88 mmol/l (P less than 0.001) was observed in male Sprague-Dawley rats treated for 11 days with isotretinoin (oral dosing; 10 mg/day). This rise was due to an increased level of plasma very low density lipoproteins (VLDL). When VLDL from untreated rats were labeled with 125I-labeled tyramine-cellobiose and injected intravenously into rats treated for 10 days with isotretinoin (n = 6) and in control rats (n = 6), it was found that the disappearance of radioactivity from the blood was dramatically retarded in the treated animals. The disappearance could be divided into two phases, a rapid (alpha) phase dominated the first 5 min and was followed by a slower (beta) phase. The half-life of the beta-phase increased significantly from 53 +/- 7 min in the controls, to 120 +/- 62 min after isotretinoin. VLDL prepared from isotretinoin-treated animals (n = 6) had about the same half-life in control animals (62 +/- 8 min) as had ordinary VLDL. The elimination of tracer from the blood was mainly due to uptake by the liver. The amount of radioactivity in the liver after 30 min of circulation was significantly reduced from 34 +/- 7% of injected dose in controls to 24 +/- 5% in the isotretinoin group (P = 0.013). The uptake in other organs was less than 3% per organ and was essentially unaffected by the treatment.(ABSTRACT TRUNCATED AT 250 WORDS)