Regulation of lipoprotein lipase immunological study of adipose tissue

An antibody to purified rat heart lipoprotein lipase was used to determine the relative specific activities of adipose tissue lipoprotein lipase from fed and fasted rats. The antibody was immobilized by coupling it to a Sepharose gel. This antibody bound approx. 80% of the lipoprotein lipase activity of extracts of rat adipose tissue. When the extracts were separated by gel chromatography into two lipase activity fractions (lipoprotein lipase "a" and lipoprotein lipase "b") and these fractions incubated with the antibody, only 10% of the lipoprotein lipase "a" activity was bound by the highest antibody concentration employed, whereas 93% of the lipoprotein lipase "b" was bound by the same amount of antibody. Increasing amounts of antibody incubated with extracts of adipose tissue of fed or fasted rats yielded similar titration curves. When a constant amount of antibody was incubated with increasing amounts of the adipose extracts, no significant difference was noted between extracts from fed and fasted animals. The data indicate that the high lipoprotein lipase activity of adipose tissue of fed rats, compared with that of rats fasted overnight, results from the presence of more lipoprotein lipase protein.