Zappia G C, Steiner M, Ando Y, Baldini M
Transfusion. 1976 Mar-Apr;16(2):122-9. doi: 10.1046/j.1537-2995.1976.16276155105.x.
Exposure of platelets to 1 C led to a transient increase in cyclic AMP levels (determined either by a protein binding method or by radioimmunoassay) within five to ten minutes reaching a maximum 10 to 15 minutes after chilling was begun and returning subsequently to baseline values. Addition of EDTA to the platelet suspension medium prevented this increase. Rewarming at 37 C produced a sudden reduction in platelet cyclic AMP. To determine whether the cold-induced increase in cyclic AMP was due to a transient stimulation of platelet adenylate cyclase or a rapid inhibition of phosphodiesterase, these enzymes were assayed in ruptured platelet suspensions. Platelet adenylate cyclase activity was found to possess certain characteristics similar to those of the enzyme derived from other sources but there was a marked potentiation of fluoride-stimulated adenylate cyclase activity by 0.001 M EDTA. This effect was limited to low EDTA concentrations. Exposure of platelets to 1 C for up to 60 minutes did not increase adenylate cyclase activity but lowered it substantially compared with controls kept at room temperature. Phosphodiesterase activity at 1 C was depressed sooner and to a greater extent than was adenylate cyclase. The transient rise in cyclic AMP levels in chilled platelets appears to be due to a disproportionate reduction of cyclic nucleotide phosphodiesterase activity.
将血小板暴露于1℃会导致环磷酸腺苷（cAMP）水平在5至10分钟内短暂升高（通过蛋白质结合法或放射免疫测定法测定），在开始冷却后10至15分钟达到最大值，随后恢复到基线值。向血小板悬浮培养基中添加乙二胺四乙酸（EDTA）可阻止这种升高。在37℃复温会使血小板cAMP突然降低。为了确定冷诱导的cAMP升高是由于血小板腺苷酸环化酶的短暂刺激还是磷酸二酯酶的快速抑制，在破裂的血小板悬浮液中对这些酶进行了测定。发现血小板腺苷酸环化酶活性具有与来自其他来源的酶相似的某些特性，但0.001 M的EDTA对氟化物刺激的腺苷酸环化酶活性有明显的增强作用。这种作用仅限于低浓度的EDTA。将血小板暴露于1℃长达60分钟不会增加腺苷酸环化酶活性，但与保持在室温的对照相比会使其大幅降低。在1℃时磷酸二酯酶活性比腺苷酸环化酶更快且更显著地受到抑制。冷却的血小板中cAMP水平的短暂升高似乎是由于环核苷酸磷酸二酯酶活性不成比例的降低。
