Induction of heat shock protein 70 mRNA in adult hamster facial nuclear groups following axotomy of the facial nerve.

In this study, the effects of axotomy on heat shock protein 70 (hsp70) mRNA levels were analyzed by northern blot hybridization with a mouse-inducible hsp70 cDNA probe. The right facial nerve of adult golden hamsters was axotomized external to the skull, with the left nerve serving as sham-operated and internal control. Postoperative survival times were 0.5, 2, 6, 12, and 24 hr, with three to six animals per time point. Total RNA in the axotomized and control facial nuclear groups, dissected from the brain stem, was isolated by guanidinium-thiocyanate extraction and analyzed by northern hybridization and scanning densitometry. For normalization, the blots were rehybridized with a genomic cDNA probe complementary to the 28 S rRNA. At 0.5 hr postoperative, there was a 68% induction of hsp70 mRNA levels as compared to control. This increase peaked at 2 hr postoperative with a 280% induction and declined subsequently to 160% at 6 hr, 33% at 12 hr, and -56% at 24 hr, relative to control levels. As a positive control, hyperthermia-induced hsp70 expression was established in hamster whole brain using northern blot hybridization and the mouse-inducible hsp70 cDNA probe. There was a 126% increase in hsp70 mRNA levels relative to control at 1.5 hr following hyperthermia. By 6.5 hr after the 1.5-hr hyperthermic period, there was a 40% decrease in hsp70 mRNA levels below control. The results provide the first evidence that peripheral axotomy acts as a cell stressor to induce the expression of hsp70 mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)