N-(4-hydroxyphenyl)retinamide (fenretinide) induces retinol-binding protein secretion from liver and accumulation in the kidneys in rats.

The chemopreventive retinoid N-(4-hydroxyphenyl)retinamide (HPR) depresses serum retinol and retinol-binding protein (RBP) concentrations. To study long-term effects of HPR on serum proteins, rats were fed a control diet or a diet containing HPR (737 mumol/kg diet) for 14 d. Serum retinol and RBP of HPR-treated rats decreased to 42 and 41%, respectively, of initial concentrations. Transthyretin, albumin and transferrin did not differ between treatments. Previous studies found that HPR decreased secretion of the retinol-RBP complex into plasma. To investigate acute effects of HPR on RBP metabolism, vitamin A-deficient rats were injected with HPR (51 mumol/kg body wt), retinol (0.52 mumol/rat) or Tween carrier only. Liver RBP concentrations in HPR- and retinol-treated rats were 45 and 18%, respectively, of concentrations in Tween-treated rats, indicating rapid RBP secretion. Tween- and HPR-treated rats maintained relatively constant serum RBP concentrations, whereas retinol-replete rats had 12-fold higher serum RBP after 150 min. Rats treated with HPR and rats treated with retinol had 29- and eightfold higher kidney RBP concentrations, respectively, than Tween-treated rats, indicating rapid clearance of RBP from plasma. We conclude that HPR affects RBP metabolism by inducing secretion of liver RBP into the bloodstream and rapid RBP accumulation in the kidney.

Schaffer EM ，Ritter SJ ，Smith JE 《JOURNAL OF NUTRITION》

Secretion of vitamin A and retinol-binding protein into plasma is depressed in rats by N-(4-hydroxyphenyl)retinamide (fenretinide).

Smith JE ，Lawless DC ，Green MH ，Moon RC ... -  《JOURNAL OF NUTRITION》

Retinol-binding protein secretion from the liver of N-(4-hydroxyphenyl) retinamide-treated rats.

Ritter SJ ，Smith JE 《-》

Secretion of N-(4-hydroxyphenyl) retinamide-retinol-binding protein from liver parenchymal cells: evidence for reduced affinity of the complex for transthyretin.

The synthetic retinoid 4-HPR has been shown to markedly lower the plasma concentration of both retinol and RBP in rats and humans. We have studied the effect of 4-HPR on the secretion of retinol-RBP from liver cells in vivo and in vitro. In rats maintained with a normal diet, a vitamin A-deficient diet or a normal diet supplemented with 4-HPR, chylomicrons [3H]retinyl esters were rapidly cleared from the plasma. The secretion of chylomicron-derived [3H]retinol from tissues to the circulation, however, was different. In control rats, the lymph-derived [3H]retinol peaked after about 2 hr, whereas 4-HPR treatment effectively reduced this peak of [3H]retinol. Our results suggest that 4-HPR inhibits secretion of retinol-RBP from the liver. Therefore, we decided to study the effect of 4-HPR on the secretion of RBP using the human hepatoma cell line HepG2. Retinol and 4-HPR were found to induce the secretion of RBP. The medium from cells treated with 4-HPR was immunoprecipitated with antibodies against human RBP. HPLC analysis of the precipitated RBP revealed the presence of 4-HPR. When the medium from cells incubated with either 4-HPR or retinol was applied to a TTR affinity column, we found that RBP from cells incubated with 4-HPR had a considerably reduced affinity for TTR. We conclude that 4-HPR binds RBP and thereby induces secretion of RBP in HepG2 cells, and that the secreted 4-HPR-RBP complex has a reduced affinity for TTR. This observation may explain the 4-HPR-induced reduction of plasma retinol and RBP observed in in vivo studies.

Holven KB ，Natarajan V ，Gundersen TE ，Moskaug JO ，Norum KR ，Blomhoff R ... -  《INTERNATIONAL JOURNAL OF CANCER》

Effects of N-(4-hydroxyphenyl)retinamide on vitamin A metabolism in rats.

Adams WR ，Smith JE ，Green MH 《-》