Methionine metabolism via the transamination pathway in rat liver.

After incubation, the triacylglycerol-rich lipoproteins seen under the electron microscope appeared as partially degraded structures with atypical, discoid, flattened and lamellar forms. As shown in Table 1, heparin produced a significant increment in the hydrolysis of 3H-labelled esterified fatty acids and 14C-labelled acylglycerol glycerol from the 3Hand 14C-labelled triacylglycerol-rich lipoproteins in the medium. A significant proportion of the hydrolysed labelled lipids appeared incorporated into the tissue lipids at the end of incubation. Most of the 3H-labelled fatty acids appeared in their esterified form, whereas the I4C taken up by the tissue appeared distributed in unesterified fatty acids, esterified fatty acids and acylglycerol glycerol. The present results show that adipose tissue in uitro is able to utilize not only the fatty acids but also the glycerol moiety released by the action of lipoprotein lipase on the lipoprotein triacylglycerol. This effect is quantitatively small but effective, agreeing with the reported ability of adipose tissue to metabolize glycerol (Chaves & Herrera, 1978; Herrera & Ayanz, 1972). It may be significant in situations of hyperlipidaemia in the presence of augmented adipose-tissue lipoprotein lipase and glycerokinase activities, as in obesity (Rath et al., 1974; Treble & Mayer, 1963).