Immunoelectron microscopic study of tubulin and microtubule-associated proteins after transient cerebral ischemia in gerbils.

Differential vulnerability of microtubule components to cerebral ischemia has been reported previously. We investigated the disintegration of microtubules using immunoelectron microscopy for alpha-tubulin and microtubule-associated protein 1A and 2 (MAP1A and 2). Mongolian gerbils were subjected to bilateral carotid occlusion for 10 to 30 min and reperfusion for up to 72 h following ischemia for 10 min. After ischemia for 10 min, some dendrites in the stratum moleculare of the subiculum-CA1 region lost immunoreaction products for alpha-tubulin and MAPs. Loss of the reaction products spread to the medial CA1 region during progressive ischemia for 30 min. In some dendrites, electron-dense precipitates for MAPs were dispersed in the dendritic cytoplasm with little reaction product on microtubules and without alteration of the reaction for alpha-tubulin. After recirculation, loss of electron-dense precipitates for alpha-tubulin and MAPs, as well as disintegration of microtubules, propagated further to the medial CA1 region and to the proximal dendrites. The present study demonstrated prompt disintegration of microtubules with rapid disappearance of the reaction for MAPs which seemed to be caused by detachment of MAPs from the microtubule cores.