Hsp expression in toad red blood cells is unrelated to changes in ambient temperature

Abstract

Heat shock proteins (particularly Hsp70) and other components of the stress-response system in the nucleated erythrocytes of a cold resistant (Bufo viridis) and cold sensitive (B. regularía) toads were investigated. Toads are terrestrial and poikilothermic, they are vulnerable and constantly exposed to diverse ambient temperatures, both in short-term (daily changes in temperature) and in long-term (seasonal changes). It was found that Hsp70 in red blood cells of the two species of toads is expressed variably and in relatively high levels at controlled room temperature. Comparable levels of Hsp70 were observed in the two species under a variety of ambient conditions. The formation of heat shock factor 1 -heat shock element binding complex, considered a first step in the stress-response system was unconnected to thermal conditions. Although toads prove to possess the components involved in the cellular stress-response, the relationships and regulation of this system are substantially different from the regular response of the system in mammals. The high levels of resting Hsp70 in toad erythrocytes could be beneficial in facilitating survival in variable thermal and stress conditions. This hypothesis is supported by the different responses observed to cold shock in two exemplary species, a homeotherm (chicken, Gallus domesticus) and a poikilotherm (lizard, Agama stelio). It is suggested that a cellular strategy of maintenance at a high level of Hsp70 is predominant in vulnerable species, and makes them prepared for temperature changes and unpredictable stress stimuli that may interfere with appropriate cellular functions.

Hsp levels in toad heart are independent of temperature and pharmacological stimuli

“…Investigation of the cardiac activity of the two species did not disclose a distinct difference between the two species (Chapovetsky & Katz 2003), and therefore other differences were sought that could elucidate the basis for the temperature resistance of one of these species. This study extends a previous one on the effect of temperature on the Hsp70 level of red blood cells (Chapovetsky & Katz 2005). In the face of the radical difference in temperature sensitivity of the two species, in this paper we attempted to look at the possible influence of or correlation between temperature and physiological parameters of heart activity and Hsp70 regulatory mechanisms at the cellular and molecular levels.…”

“…The lower panel compares the level of Hsp70 in the samples by densitometry (using TINA; see methods). The level of Hsp70 in heart tissue of both species was many times higher, compared with either Hsp70 level detected in skeletal muscle (Figure 1), or in erythrocytes (Chapovetsky & Katz 2005). This and other experiments were repeated several times with similar results showing high variability which precluded a meaningful statistical analysis.…”

“…The latter species becomes paralyzed and dies within a few hours upon exposure to temperatures below 7uC (Katz & Gil 1997). In this and a previous study (Chapovetsky & Katz 2005) an effort was made to find out whether the stress-induced Hsp proteins could be implicated in explaining this difference. Since no direct correlation could be established between temperature and levels of Hsp70 in erythrocytes (Chapovetsky & Katz 2005), the effect of other stresses, i.e.…”

“…In this and a previous study (Chapovetsky & Katz 2005) an effort was made to find out whether the stress-induced Hsp proteins could be implicated in explaining this difference. Since no direct correlation could be established between temperature and levels of Hsp70 in erythrocytes (Chapovetsky & Katz 2005), the effect of other stresses, i.e. hypoxia and hypoxic agonists, was investigated on the expression of this system in heart and muscle tissues.…”

“…This antibody was also used in a previous study on the toads' erythrocytes (Chapovetsky & Katz 2005) and was tested in addition on lizard and chick eythrocytes. Figure 5 in that paper shows that this anti Hsp70 antibody detected specifically changing levels and dynamics of Hsp70.…”