Relationship between plasma triglyceride concentration and adipose tissue lipoprotein lipase activity in rats of...

Plasma triglyceride (TG) concentration and adipose tissue lipoprotein lipase (LPL) activity was determined in male and female rats aged 40 days, 100 days and 1 year. Plasma TG levels increased with age in both sexes, but the rate of rise was greater in female as compared to male rats. As a consequence, plasma TG levels, which were lower in 40 and 100 day old female rats, were similar in both sexes at 1 year. Adipose tissue LPL activity, measured at the same time of day as were plasma TG levels, did not vary as a function of either age or sex. On the other hand, when adipose tissue LPL activity was measured in the early morning, just after rats had finished eating, there was a marked increase in the activity of 40 day old rats of either sex. This dietary-induced rise in adipose tissue LPL activity following eating was not seen in 100 day and 1-year-old rats. Thus, changes in adipose tissue LPL activity cannot account for previously described effects of age and sex on plasma TG concentration.