Glycogen Synthetase Activity in Blood Platelets

Studies on Human Platelets Stored at 20–22°C without Agitation

“…After incubation at 37 °C for 20 min the labeled glycogen was isolated, purified, solubilized in bidistilled water and used for the radioactivity counting [29], The transglucosylase-specific activity (cpm mg protein -1 h "1) of each fraction was expressed as percentages of the total in the four fractions. Results represent mean values obtained in three experiments and are expressed as percentages of the maximum measured at day 0 of storage.…”

“…The two variants of platelet transglucosylase EC 2.4.1.11: D (b), dependent from glucose-6-phosphate (G6P) and 'I' (an indepen dent on G6P, were determined in the four platelet populations as previously de scribed [29]. The glycogen content was estimated according to the method of Seifter el al.…”

“…The glycogen content was estimated according to the method of Seifter el al. [29] by using a glucose solution as the standard. The transglucosylase specific activity (counts, mg protein min"1) was expressed as percentages of the total in the four fractions.…”

Glycogenesis and glyconeogenesis in human platelets

“…This preparation was stable for several hours at 0C, losing variable degrees of activity after storage overnight at 4GC. The final assay cuvette concentration contained 50-100 ,L/ ml platelet extract, 0.46 mm NADP, 0.1-2 mm fructose-1,6-diphosphate, 4 Aeg/ml glucose 6-phosphate dehydrogenase, 16 jig/ml hexose isomerase, and 20 mm MSH, in 50 mM Tris buffer, pH 7.5 (10). For orthophosphate release experiments, an assay was employed which was described previously (3).…”

Platelet Function

“…These events include aggregation [156,199], phagocytosis [162,201], clot retraction [198,199], and release reactions [197]. Furthermore, energy is required for active uptake of substances such as serotonin [240,256,298,314], production of glycogen [261,287], fatty acids [72,110,169,172], proteins [23,24,57,157,292] and phospholipids [165]. The energy source is ATP.…”