Swine microsomal acyl-CoA synthetase activity: effect of age and diet

Fatty acid activation was examined by assessing the activity of acyl-CoA synthetase (ACS) in microsomal fractions of liver and adipose tissue obtained from swine of various ages. Liver ACS activity increased from ca. 200 to 800 nmol/(minute x g tissue) between birth and 25 days postpartum; enzyme activity generally remained elevated postweaning through 155 days of age. The preweaning hepatic patterns on a wet weight and protein basis were similar, but the wet weight- and protein-based patterns diverged after weaning due to an increase in microsomal protein. As in liver, adipose tissue ACS activity rose rapidly from birth to 25 days of age [20-110 nmol/(minute x g tissue)] but declined to lower levels after weaning. Expression of enzyme activity on a wet weight, protein, or cellular basis revealed similar developmental patterns for adipose tissue. The postweaning fall in adipose tissue ACS activity was partially explained by decreasing cellularity per unit tissue weight. In swine fed equal amounts of isoenergetic-isonitrogenous diets with low or high fat content, hepatic ACS activity tended to increase in pigs fed the high fat diet with no effect of diet on the adipose enzyme. Starvation elevated liver ACS activity, whereas the adipose enzyme activity was marginally decreased.