Abnormal platelet glycogen metabolism in multiple myeloma patients.

This study presents evidence on the occurrence of an inverse relationship between activation of glycogen synthetase and inactivation of phosphorylase in a platelet preparation in vitro. The activities of glycogen synthetase and phosphorylase and the pattern of changes in these activities in platelets from controls and multiple myeloma patients were compared. Platelets obtained from multiple myeloma patients were shown to have an increased glycogen content, accompanied by an elevated level of glycogen synthetase a and a decreased activity of phosphorylase a. The pattern of changes in these enzyme activities during incubation was also different in platelets of controls and multiple myeloma patients. Extracts from patients' platelets prevented glycogen synthetase activation and phosphorylase inactivation of control platelets. Preincubation of platelets from multiple myeloma patients in control plasma resulted in an increased rate of glycogen synthetase activation, and abolished activation of phosphorylase which was found after preincubation in autologous plasma.