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Effects of deteriorated frying oil and dietary protein levels on liver microsomal enzymes in rats
Author(s) -
Huang ChingJang,
Cheung NamSang,
Lu VenRond
Publication year - 1988
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02542385
Subject(s) - microsome , chemistry , transaminase , medicine , endocrinology , biochemistry , enzyme , biology
This study was conducted to investigate the effects of deteriorated used frying oil (DUFO) and dietary protein levels upon the hepatic microsomal drugmetabolizing enzyme system. Fresh soybean oil was subjected to a deep‐frying process at 205±5°C for four six‐hr periods. The resultant DUFO was incorporated into high protein (HU) (27% lactalbumin) or low protein (LU) (8% lactalbumin) test diets at a 15% level. High protein (HF) and low protein (LF) diets containing fresh soybean oil served as the control. Male Long‐Evans young rats fed the test diets for eight weeks showed decreased fat absorption and increased red blood cell (RBC) in vitro hemolysis. The activities of hepatic aminopyrine N‐demethylase (AD), aniline hydroxylase (AH), NADPH‐cytochrome C reductase (NCD), UDP‐glucuronyl transferase (UDPGT) and glutathione S‐transferase (GST) as well as cytochrome P‐450 content were significantly increased in rats fed the HU diet. However, the AD, AH and GST activities, as well as the cytochrome P‐450 content of the LU group, were increased to a lesser extent and significantly lower than those of the HU group. Rats fed the LU diet were the only group that showed significantly elevated serum GOT (E.C. 2.6.1.1, glutamate‐oxaloacetate transaminase) and GPT (E.C. 2.6.1.2, glutamatepyruvate transaminase) values. Supplementation of 0.3% DL‐methionine to the HU diet further increased GST activity. Unexpectedly, rats fed the low protein control diet (LF) also had raised levels of AD, AH and UDPGT activities as well as in vitro RBC hemolysis. It was concluded that rat hepatic microsomal enzymes are induced by dietary DUFO and that the level of induction is influenced by dietary protein level.