TI - alphaB-crystallin is phosphorylated during myocardial infarction : involvement of platelet-derived growth factor -BB . AB - alphaB-crystallin is the most abundant low-molecular-weight heat shock protein in heart and recent studies have demonstrated that it plays a cardioprotective role during myocardial infarction both in vivo and in vitro . On the other hand , platelet-derived growth factor ( PDGF ) , a potent serum mitogen , has been reported to improve cardiac function after myocardial infarction . In the present study , using a mouse myocardial infarction model , we investigated whether alphaB-crystallin is phosphorylated during myocardial infarction and the implication of PDGF-BB . Phosphorylation of alphaB-crystallin at Ser-59 was time dependently induced and plasma PDGF-BB levels were concomitantly increased . Moreover , PDGF-BB -stimulated phosphorylation of alphaB-crystallin was suppressed by SB203580 , a specific inhibitor of p38 mitogen-activated protein ( MAP ) kinase , in primary cultured cardiac myocytes . Our results indicate that PDGF-BB induces phosphorylation of alphaB-crystallin via p38 MAP kinase during myocardial infarction .