Responsiveness of early embryos to environmental insults: potential protective roles of HSP70 and glutathione

• Published in: Theriogenology Vol. 55; no. 1; pp. 209 - 223
• Main Authors: Edwards, J.L., King, W.A., Kawarsky, S.J., Ealy, A.D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 2001
• Subjects: Animals; Cattle - embryology; embryo; Embryo, Mammalian - physiology; Environment; Female; glutathione; Glutathione - physiology; heat shock; Hot Temperature; HSP70; HSP70 Heat-Shock Proteins - physiology; Male; Sex Characteristics; sex differences; Stress, Physiological; thermotolerance; Time Factors; embryo; heat shock; HSP70; thermotolerance; glutathione; sex differences
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/S0093-691X(00)00455-6

Early embryos are not as passive as previously thought. In the bovine, embryos as early as the 2-cell stage can respond to environmental insults at both the cellular and molecular level by altering expression of specific genes and synthesis of proteins. Moreover, sex related differences exist in how early embryos respond to otherwise hostile environments. As aggressive as early embryos may be to tolerate environment insults, the majority will fail to continue in development. Reduced developmental potential of embryos exposed to elevated temperatures is likely due to direct effects on the early embryo. However, as embryos proceed in development they acquire the ability to better withstand environmental insults. Developmental acquisition of tolerance to environmental stress may be contingent upon acquisition of protective biochemical mechanisms or simply due to increased cell numbers. Correlative evidence has suggested a potential role of heat shock protein 70 and glutathione for protection of embryos in face of elevated temperature. Of these two possibilities, HSP70 appears least likely to play a significant role in developmental acquisition of thermotolerance. Bovine embryos as early as the 2-cell stage, are able to mount a heat shock response; a developmental stage that is most sensitive to elevated temperatures. A more likely candidate for conferring increased resistance of early embryos to elevated temperature is glutathione.