Differences in activity of hepatic microsomal triglyceride transfer protein among species

Five sows, five cows, five hens, six guinea pigs, six rabbits, and six rats were used in a study to determine if hepatic microsomal triglyceride trans fer protein activity differed among species that varied in site of fatty ac id synthesis and rate of hepatic triglyceride export. No differences in pla sma nonesterified fatty acids were seen among species. Plasma concentration s of glucose were highest in the hen, intermediate in the rat, guinea pig, and rabbit and lowest in the sow and cow. Liver triglyceride was low in all species with the only significant difference being between the hen and the guinea pig (4.7 and 1.1%, DM basis, respectively). No microsomal triglycer ide transfer protein activity was found in muscle. The cow, rat, and guinea pig had the lowest levels and the hen and rabbit the highest levels of duo denal microsomal triglyceride transfer protein activity. Hepatic microsomal triglyceride transfer protein activity was significantly higher in the sow than the other species. Hepatic microsomal triglyceride transfer protein a ctivity was 1.51, 1.63, 2.36, 2.72, 2.95, and 6.70 nmole triolein transferr ed/h/mg microsomal protein for the guinea pig, rabbit, cow, rat, hen, and s ow, respectively. Microsomal triglyceride transfer protein activity in duod enal tissue was 18.0, 18.6, 19.2, 33.4, 113, and 161% of hepatic microsomal triglyceride transfer protein activity for the sow, cow, rat, guinea pig, hen, and rabbit, respectively. Hepatic microsomal triglyceride transfer pro tein activity scaled to liver weight and metabolic body size was 2.69, 3.36 , 4.58, 5.83, 7.49, and 22.3 nmole triolein transferred in the liver/min/kg body weight(0.75) for the rabbit, guinea pig, rat, hen, cow, and sow, resp ectively. There was little relationship between previously published rates for triglyceride export and hepatic microsomal triglyceride transfer protei n activity measured in this experiment. (C) 1999 Elsevier Science Inc. All rights reserved.