Nuclear transition of heat shock protein in guinea pig cochlea after hyperthermia

The main reaction of heat shock protein (hsp) 70 family to heat shock is 2-fold, one is an increased synthesis in the cytoplasm and the other is a transition from the cytoplasm to the nucleus. Although the former has been already reported in the cochlea by several authors, there has been no description as to the latter. The present study was designed to determine whether this nuclear transition of hsp70 family is also present in the cochlea as in the other organs. Albino guinea pigs subjected to hyperthermia treatment (42 degrees C, 10 min) were killed at 0, 6, 18 or 24 h after the cessation of hyperthermia treatment. Immunohistochemical studies in the cochlea of the untreated animals revealed anti-hsp70 family immunoreactivity mainly in the cytoplasm of the various cells in the cochlea, including the interdental cells, the spiral ganglion cells or the outer hair cells. However, immunoreactivity remarkably increased in the nucleus immediately after the cessation of hyperthermia treatment and this increased immunoreactivity disappeared at 6 h or later. It is concluded that the nuclear transition of hsp70 family also takes place under hyperthermal stress in the cells of the cochlea as in other organs.