Powerful Stimulation by Formaldehyde of Platelet Functions

Low concentrations of formaldehyde (HCHO) increased both the rate and the extent of thrombin-induced secretion of ATP, ADP, preabsorbed 14C-serotonin, β-N-acetyl glucosaminidase and β-galactosidase from gel-filtered human platelets (GFP). The effect was optimal (7-fold stimulation) with 0.03-0.07 u/ml of thrombin; above 0.1 u/ml there was little effect. With 0.05 u/ml of thrombin maximal stimulation was seen with 0.03-0.5 mM HCHO while the aldehyde was inhibitory above 1 mM. The degree of stimulation increased with the time of exposure of the platelets to HCHO and was maximal after 15-20 min. (37°C). Incubation of control GFP (without HCHO) at 37°C caused a progressive increase in the secretory response 2-3 fold above preincubation values. The degree of stimulation was not altered by indomethacin or aspirin suggesting that prostaglandin/thromboxane formation was not involved.HCHO (0.3 mM) caused a progressive reduction in the steady-state level of metabolic ATP which leveled off after 15-20 min. of incubation. There was no change in the adenylate energy charge, but HCHO caused a transient increase in lactate production in the presence of antimycin A. Similar results were obtained with ADP and epinephrine as inducers of serotonin and adenine nucleotide secretion while the response to collagen was abolished by these low HCHO concentrations. The primary and secondary aggregation responses to ADP and epinephrine, which had been markedly depressed by GFP maintained at 37°C for longer periods of time, was restored by exposure to HCHO. The mechanism of activation, preservation and restoration of platelet activities by HCHO is obscure.