Hsp70 in bovine lenses during temperature stress.

Purpose: To determine the effects of heat shock treatment on cold cataract formation in bovine lenses. METHODS: A laser scanning system (ScanTox(TM)) was used to analyze the optical quality of bovine lenses during a cooling and warming cycle. Cycloheximide, a compound that prevents new protein synthesis was used to inhibit inducible heat shock protein 70 (Hsp70) production during heat stress. Cycloheximide was also used to verify that the induction of Hsp70 takes place in lenses during heat stress. Western blots determined the relative accumulation of Hsp70 in urea soluble lens fractions. Lenses from animals approximately 2 years of age (n=60) were used in this experiment. Results: The decrease in relative light transmittance during cold cataract varies for each group of lenses, with the greatest decrease appearing in the heat shock group in culture medium and the least in the control groups and the heat shock group with cycloheximide. The primary result is that heat shock lenses were most affected by the cold cataract (57% decrease in intensity of refracted beam), and that this effect is prevented by cycloheximide. Western blot results show an increase of Hsp70 with heat shock in the urea soluble lens fractions. Conclusions: The results show that heat shock treatment increased both light scattering and the presence of Hsp70. Also cycloheximde prevented both the heat shock effect and the expression of Hsp70 in bovine lenses.