Heterogeneity of Human Platelets III. GLYCOGEN METABOLISM IN PLATELETS OF DIFFERENT SIZES

Abstract

Summary Glycogenolysis, glycogenesis, glyconeogenesis and the enzymes phosphorylase, glycogen synthetase, and fructose‐1–6‐diphosphatase were investigated in heavy and light platelet populations in order to determine the presence or extent of metabolic heterogeneity. The mean volume of the heavy platelets was approximately 2.4‐fold greater than that of the light platelets. Heavy platelets contained 3.4‐fold more glycogen and had a 5.9‐fold greater rate of glycogenolysis per g wet weight, than light platelets. Heavy platelets incorporated 5.9‐fold more [¹⁴C]glucose into platelet glycogen when data were expressed per g wet weight, and 1.7‐fold more [¹⁴C]glucose when data were expressed per μmole of glycogen. This difference in glycogen synthesis was paralleled by a 1.8‐fold greater glycogen synthetase activity. Heavy platelets incorporated 3.0‐fold more [¹⁴C]citrate into platelet glycogen when data were expressed per g wet weight, and 1.4‐fold more [¹⁴C]citrate when data were expressed per μmol of glycogen. Similar results were obtained utilizing [¹⁴C]pyruvate as precursor. This difference in glyconeogenesis was paralleled by a 2.5‐fold greater fructose‐1–6‐diphosphatase activity for heavy platelets.