Modification of actions of heat shock on development and apoptosis of cultured preimplantation bovine embryos by oxygen concentration and dithiothreitol

• Published in: Molecular reproduction and development Vol. 75; no. 8; pp. 1338 - 1350
• Main Authors: de Castro e Paula, L.A., Hansen, P.J.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-08-2008; Wiley-Liss
• Subjects: Animals; apoptosis; Apoptosis - drug effects; Apoptosis - physiology; Benzimidazoles; Biological and medical sciences; Blastocyst - drug effects; Blastocyst - physiology; Cattle; development; Dithiothreitol - pharmacology; embryo; Embryology: invertebrates and vertebrates. Teratology; Embryonic Development - drug effects; Embryonic Development - physiology; Fundamental and applied biological sciences. Psychology; General aspects; General aspects. Development. Fetal membranes; heat shock; Hot Temperature; In Situ Nick-End Labeling; oxygen; Oxygen - metabolism; Shock; Embryo; Reactive oxygen species; Oxygen; Blastocyst; Ox; heat shock; Antioxidant; In vitro; Vertebrata; Heat; Mammalia; Animal; Development; Artiodactyla; Ungulata; Apoptosis
• ISSN: 1040-452X; 1098-2795
• DOI: 10.1002/mrd.20866

Preimplantation embryos exposed to elevated temperatures have reduced developmental competence. The involvement of reactive oxygen species in these effects has been controversial. Here we tested hypotheses that (1) heat shock effects on development and apoptosis would be greater when embryos were cultured in a high oxygen environment (air; oxygen concentration = ∼20.95%, v/v) than in a low oxygen environment (5% oxygen) and (2) that these effects would be reversed by addition of the antioxidant dithiothreitol (DTT). Heat shock of 41°C for 9 hr reduced development of two‐cell embryos and Day 5 embryos to the blastocyst stage embryos when in high oxygen. There was no effect of heat shock on development when embryos were in low oxygen. Furthermore, induction of TUNEL‐positive cells in Day 5 embryos by heat shock only occurred when embryos were in high oxygen. Addition of DTT to two‐cell embryos either did not reduce effects of a heat shock of 41°C for 15 hr on development or caused slight protection only. In contrast, treatment of Day 5 embryos with DTT reduced effects of heat shock on development and apoptosis. In summary, oxygen tension was shown to be a major determinant of the effects of heat shock on development and apoptosis in preimplantation bovine embryos. Protective effects of the antioxidant DTT were stage specific and more pronounced at later stages of development. Mol. Reprod. Dev. 75: 1338–1350, 2008. © 2008 Wiley‐Liss, Inc.