INDUCTION OF HEAT-SHOCK (STRESS) PROTEIN-70 AND ITS MESSENGER-RNA IN THE NORMAL AND LIGHT-DAMAGED RAT RETINA AFTER WHOLE-BODY HYPERTHERMIA

In situ hybridization and immunocytochemistry were used to investigate the distribution of the 70 kDa heat shock or stress protein (hsp70) a nd its mRNA in specific layers of the retina of adult rats at 0, 4, 18 , and 48 or 50 hr after a brief whole body hyperthermic treatment. Ind uction of hsp70 mRNA was noted in the photoreceptor layer of the retin a within 4 hr after hyperthermia. Pronounced accumulation of inducible hsp70 immunoreactivity was observed in cytoplasmic extensions of the photoreceptor cells, especially the inner segment zone which attained peak levels at the 18 hr time point. Selective destruction of photorec eptors by light damage prior to hyperthermia inhibited the post-hypert hermic rise in newly synthesized retinal hsp70. Our results suggest th at the photoreceptor cell layer is the primary site of synthesis of hs p70 in the rat retina and that the greatest increase in hsp70 immunore activity following such a hyperthermic stress occurs in that layer. Th is stress response of the photoreceptors is discussed in relation to t heir location and function in the retina. (C) 1994 Wiley-Liss, Inc.