Red blood cell Hsp 70 mRNA and protein as bio-indicators of temperature stress in the brook trout (Salvelinus fontinalis)

Abstract

The purpose of this study was to examine the heat shock protein (Hsp) 70 mRNA and protein response in several tissues of Miramichi brook trout (Salvelinus fontinalis) under both acute and extended heat stress conditions to determine the utility of the red blood cell (rbc) heat shock response as a biomarker of sublethal temperature stress. Red blood cells consistently produced one of the highest responses of all of the tissues examined. Recovery of Hsp 70 mRNA following acute temperature increase required between 24 h and 48 h. In contrast, Hsp 70 protein levels remained significantly elevated for more than 48 h after the heat stress was terminated. During a 6-day extended (23°C) heat stress, rbc Hsp 70 mRNA returned to control levels between 72 and 144 h, whereas Hsp 70 protein was still significantly elevated after 6 days. Thus, although Hsp 70 mRNA proved to be a more sensitive indicator of heat stress in all tissues examined, Hsp 70 protein levels were more sustained. This study confirms the utility of rbcs as a biomarker tissue of thermal stress in fish and indicates that water temperatures presently being reached in brook trout habitats in Canada are capable of inducing a significant heat shock response in this species.