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Effect of Dietary Galactose on Lysosomal Enzymes in the Chick¹

Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824

The effect of feeding diets containing toxic levels of D-galactose (50% w/w) on lysosomal enzymes in young male chicks was investigated. The total activities of ß-N-acetylhexosaminidase, ß-galactosidase, and acid phosphatase were increased in livers of chicks fed galactose by 47%, 46% and 27%, respectively, relative to corresponding activities in livers of control chicks. In contrast, no differences in lysosomal enzyme activities of chick kidney were observed between dietary groups. Liver total ß-N-acetylhexosaminidase activities increased and remained elevated during the period of consumption of the galactose-containing diet and for 2 days after transferring to the galactose-free control diet. Plasma hexosaminidase activities increased as a result of galactose feeding. Liver lysosomes from chicks fed galactose demonstrated enhanced fragility to hypo-osmotic sucrose solutions in comparison with behavior of liver lysosomes isolated from control animals. The increased lability to osmotic shock could be simulated by preincubation of lysosomes from normal chicks in solutions of high levels (50 mM) of either galactose or glucose. Diurnal variations in plasma levels of ß-N-acetylhexosaminidase of chicks raised on a 12-hour light-dark cycle (lights, 6:00 AM to 6:00 PM) were highest at 10:00 PM to 2:00 AM and lowest at 2:00 PM, whereas in the liver, they were highest at 6:00 AM and lowest at 10:00 AM.

KEY WORDS: • chick • plasma and liver lysosomal enzymes • galactose toxicity • diurnal variations

¹ This work was supported by Grant AM 10209. U. S. Public Health Service, Michigan Agricultural Experiment Station, Journal Article #6635.

² To whom inquiries should be addressed.

Manuscript received 28 January 1974.