Rat heart and skeletal muscle homogenates were compared for their intracellular lipolytic activity towards a series of saturated and unsaturated
triglycerides from
trilaurin (C12:0) to
trierucin (C22:1). It is shown that for all
triglycerides esterified with
fatty acids from C12 to C18, lipolytic activity in heart homogenates was higher than in skeletal muscle homogenates. For these
triglycerides there was no relationship between the
fatty acid chain length and the lipolytic activity. In both homogenates cleavage of unsaturated
triglycerides was higher than cleavage of the homologous saturated
triglyceride. Lipolysis of tri-delta-11-eicosenoin (C20:1) was similar in both homogenates but much lower than lypolysis of other
triglycerides. Although cleavage of
trierucin (C22:1) was very low in skeletal muscle homogenates, it was undetectable in heart homogenates, even when
enzyme concentration was increased. A mixture of
triglycerides did not show preferential hydrolysis of any simple
triglyceride.
Trierucin was the only
triglyceride that did not complete for lipolytic activity and only with heart homogenates, which shows that that
lipase(s) do not cleave
trierucin. The absence of lipolytic activity towards
trierucin in heart homogenates could explain the selective accumulation of
erucic acid-rich
triglycerides in hearts of animals fed a diet with a high
erucic acid content.