Low-temperature induction of calcium-dependent protein phosphorylation in blood platelets.

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Abstract
Exposure to low temperature causes rat platelets to change shape in a manner similar to the shape change that precedes secretagogue-induced seotonin release. Previous studies have shown that 2 proteins, of MW .apprx. 20,000 and .apprx. 40,000 become phosphorylated before secretion. Whether low temperature can induce phosphorylation of these proteins and/or serotonin secretion was investigated. Low-temperature-induced shape change has no requirement for extracellular Ca, whereas phosphorylation of the 2 proteins and subsequent serotonin release both have strong Ca requirements. Because cold treatment is though to influence platelet shape through an effect on microtubules, the events in the shape change-release sequence would be ordered as follows: microtubule disassembly .fwdarw. shape change .fwdarw. protein phosphorylation .fwdarw. secretion.