Response of Adipose Tissue Lipoprotein Lipase to Fasting in the Chicken and the Rat—A Species Difference

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Abstract
Studies were conducted to assess the influence of extraction procedures on the response of adipose tissue lipoprotein lipase (LPL) to fasting in two species, the rat and the chicken. In both cases, lipoprotein lipase was extracted more efficiently (twofold increase) from acetone powders of adipose tissue by heparin (50 units/ml) than by 25 mM NH4OH-NH4Cl. With chicken acetone powders, buffered saline solutions (1.2 M NaCl, 0.005 M Na barbital buffer, pH 6.5) were as effective as heparin solutions. Chickens fasted for 48 hours exhibited higher plasma triglyceride hydrolase, lower plasma triglycerides and higher concentrations of plasma free fatty acids than either fed or refed chickens. Total lipoprotein lipase activity of extracts of adipose tissue was not significantly affected by the nutritional state of the chicken. However, the heparin-stimulated release of LPL was significantly higher for adipose tissue slices of fed chickens than for those obtained from fasted birds. Rat serum triglyceride hydrolase activities did not differ in fed, fasted or refed groups, as it did in the chicken. Comparison of adipose tissue LPL levels in the three groups showed marked reduction of LPL in the fasted group. The method of extraction, although affecting the absolute quantities of enzyme extracted, did not affect the relative differences due to fasting or feeding.

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