Tissue and developmental variations in the heat shock response of sea lampreys (Petromyzon marinus): effects of an increase in acclimation temperature

Induction of the heat shock response (HSR) was investigated in liver, kidney and intestine tissues of Petromyzon marinus larvae (ammocoetes) acclimated to control temperatures of either 9 or 13°C. Labelling with [35S]methionine detected the enhanced synthesis of heat shock proteins (HSPs) with molecular weights of 70 kDa (HSP70) and 90 kDa (HSP90) after an abrupt elevation of water temperature. In ammocoetes maintained at 9°C, a clear induction of HSP synthesis was detected in all tissues following an increase of 20°C, and a slight induction was detected in kidney and intestine after a 15°C increase. Induction of HSP synthesis in ammocoetes acclimated to 13°C was detected after a temperature increase of 12°C in liver and kidney, and an increase of 16°C in intestine. Thus, it appears that the threshold induction temperature decreased from 29 to 25°C in ammocoete liver following an increase in acclimation temperature from 9 to 13°C. This result would be unique to lampreys, since increases in acclimation temperatures usually result in increased threshold induction temperatures in aquatic poikilotherms. The types of HSPs synthesized by liver, kidney and intestine did not change over the lamprey life cycle, suggesting that this aspect of the lamprey HSR is not regulated post-embryonically