Heat or cold chronic stress affects organ weights and Hsp70 levels in chicken embryos

This study was carried out with the objective of evaluating the effect of h eat (38.8 degreesC) or cold (35.8 degreesC) stress on chicken embryo develo pment and tissues Hsp70 levels, after the 13th day of incubation. Embryo we ight (percent egg weight), organ weight (percent embryo weight) and Hsp70 l evels (ng Hsp70 mug(-1) total protein) in different tissues (liver, breast muscle, heart, lungs, brain and kidney) were studied at the end of incubati on. Cold stress induced a lower embryo weight and lower kidney and lungs we ights, whereas heart and liver were lighter in heat-stressed embryos. An in teraction between temperature and age was obtained only for Hsp70 levels in kidney and heart. Cold-stressed embryos showed higher Hsp70 levels in the brain, lungs and liver; a decrease in brain and breast muscle Hsp70 levels was seen from the 19th to 20th days in control embryos. Hsp70 levels increa sed with age in kidneys of control embryos and in heart of heat- and cold-s tressed embryos. In conclusion, this study showed that chicken embryo organ weights are affected by incubation temperature, and that Hsp70 expression is tissue dependent (higher levels being seen in the brain) being cold-stre ss more effective in increasing Hsp70 levels in most studied tissues.