Utilization of galactose by human platelets in vitro
Horne, M.K.; Johnson, S.E.; Hart, J.S.
Journal of Laboratory and Clinical Medicine 106(3): 233-241
1985
ISSN/ISBN: 0022-2143 PMID: 3875670 Document Number: 247326
The extent to which platelets can metabolize galactose has been unknown. We have studied this question by incubating platelets with radiolabeled galactose for periods of time and analyzing the cells for radioactive metabolites. The sugar was observed to accumulate quickly in cells isolated by filtration. Within seconds at room temperature, galactose metabolites were detectable by thin layer chromatography, and within 20 minutes at 37.degree. C, radioactivity appeared in trichloroacetic acid (TCA) precipitates of the suspensions. The TCA-precipitable radioactivity was degraded by .alpha.-amylase as well as by protease. However, the TCA-soluble material released by protease digestion had an elution volume on Sepharose CL-4B too small for glycopeptides and in addition was degraded by .alpha.-amylase. The majority of the galactose metabolized by platelets, therefore, becomes incorporated into glycogen, rather than glycoprotein. The reversibility of the galactose metabolic pathway was demonstrated by the addition of an excess of the unlabeled sugar to the labeled platelets and by the effect of thrombin and collagen on the TCA-precipitable radioactivity.