Retinol and retinyl ester concentrations in rat tissues during total parenteral nutrition

Abstract

We have previously observed that continuous total parenteral nutrition (TPN) that supplies retinyl palmitate induces a strong decrease of the circulating retinol, which is associated with an impaired hepatic production of retinol-binding protein. We have investigated the effect of 7 days of TPN on the retinol and retinyl ester concentrations in rat tissues, relative to the vitamin A status [ n = 30 for vitamin A-sufficient (A +) and n = 30 for deficient (A −)]. Rats were cannulated for intravenous feeding ( n = 12 for TPN-A +, n = 12 for TPN-A −) and were compared with their per os pair-fed counterparts ( n = 12 for O-A + and n = 12 for O-A −). Retinol and retinoic acid in serum and retinol and retinyl ester concentrations in liver, kidney, lung, heart, and testis were measured by high performance liquid chromatography. TPN induced a dramatic decrease in circulating retinol of A + rats, whereas retinoic acid concentration in serum was unchanged. When TPN was given to A − rats, retinol concentration in serum remained low. Lower retinol and retinyl ester concentrations 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 + and P < 0.01 for A −). By contrast, in extrahepatic tissues, retinol and retinyl ester concentrations were similar in TPN rats compared with orally pair-fed rats. Our results indicate that TPN induced a decrease of retinol in serum and retinyl esters in liver. However, TPN was able to maintain retinol and retinyl ester concentrations in extrahepatic tissues of vitamin A-sufficient rats and to restore retinol and retinyl ester concentrations in extrahepatic tissues of vitamin A-deficient rats, albeit a low circulating retinol.