Expressions of Heat Shock and Metallothionein Genes in the Heart of Common Carp (Cyprinus Carpio): Effects of Temperature Shock and Heavy Metal Exposure

Heat shock proteins (HSPs) and metallothioneins (MTs) play important roles in protection against environmental stressors. The present study analyzes and compares the regulation of heat shock (hsp70, hsc70-1 and hsp90α) and metallothionein (MT-1 and MT-2) genes in the heart of common carp, in response to elevated temperature, cold shock and exposure to several heavy metal ions (As3+, Cd2+ and Cu2+), in whole-animal experiments. Among these metals, arsenate proved to be the most potent inducer of the examined stress genes; the hsp90α and MT-1 mRNA levels were elevated 11- and 10-fold, respectively, after a 24-h exposure. In contrast, Cd2+ at 10 mg/L had no impact on the expression of hsp90α, and the MT genes also proved to be rather insensitive to Cd2+ treatment in the heart: only a 2-2.5-fold induction was observed in response to 10 mg/L Cd2+. Heat shock resulted in a transient induction of hsp70 (19-fold) and hsp90α (15-fold), while elevated temperature had no effect on the expression of the MTs. Direct cold shock induced hsp70 expression (14-fold), while the hsp90α (26-fold) and MT-2 (2-fold) expressions peaked after the recovery period following a direct cold shock. The five stress genes examined in this study exhibited a unique, tissue-specific basal expression pattern and a characteristic sensitivity to metal treatments and temperature shocks.