RETINOL AND RETINYL ESTER CONCENTRATIONS IN RAT-TISSUES DURING TOTAL PARENTERAL-NUTRITION

We have previously observed that continuous total parenteral nutrition (TPN) that supplies retinyl palmitate induces a strong decrease of th e circulating retinol, which is associated with an impaired hepatic pr oduction of retinol-binding protein. We have investigated the effect o f 7 days of TPN on the retinal and retinyl ester concentrations in rat tissues, relative to the vitamin A status [n = 30 for vitamin A-suffi cient (A(+)) and n = 30 for deficient (A(-))]. Rats were cannulated fo r intravenous feeding (n = 12 for TPN-A(+), n = 12 for O-A(-)). Retino l and retinoic acid in serum and retinol and retinyl ester concentrati ons in liver, kidney, lung, heart, and testis were measured by high pe rformance liquid chromatography. TPN induced a dramatic decrease in ci rculating retinol of A(+) rats, whereas retinoic acid concentration in serum was unchanged. When TPN was given to A- rats, retinol concentra tion in serum remained low. Lower retinol and retinyl ester concentrat ions were measured in the livers of TPN rats compared with orally pair -fed rats, no matter the initial vitamin A status (P < 0.02 for A(+) a nd P < 0.01 for A(-)). By contrast, in extrahepatic tissues, retinol a nd retinyl ester concentrations were similar in TPN rats compared with orally pair-fed rats. Our results indicate that TPN induced a decreas e of retinol in serum and retinyl esters in liver. However, TPN was ab le to maintain retinol and retinyl ester concentrations in extrahepati c tissues of vitamin A-sufficient rats and to restore retinol and reti nyl ester concentrations in extrahepatic tissues of vitamin A-deficien t rats, albeit a low circulating retinol. (J. Nutr. Biochem. 9:316-323 , 1998). (C) Elsevier Science Inc. 1998.