BOR - Papers in Press, published online ahead of print
November 27, 2002.
Biol Reprod 2002, 10.1095/biolreprod.102.009282
BIOLOGY OF REPRODUCTION 68, 15381544 (2003)
DOI: 10.1095/biolreprod.102.009282
© 2003 by the Society for the Study of Reproduction, Inc.
Nitric Oxide Synthase Production and Nitric Oxide Regulation of Preimplantation Embryo Development
Susanne Tranguch2,
Nury Steuerwald2,3, and
Yvette M. Huet-Hudson1,2
Department of Biology,2 University of North Carolina at Charlotte, Charlotte, North Carolina 28223
A.R.T. Institute of Washington,3 Washington, D.C
Nitric oxide (NO) production plays an important role in regulating preimplantation embryo development. NO is produced from L-arginine by the enzyme nitric oxide synthase (NOS), which has three isoforms: endothelial (eNOS), neuronal (nNOS), and inducible (iNOS). It has been previously shown that inhibition of NO production by NG-nitro-L-arginine (L-NA) inhibits the development of two-cell embryos to the four-cell stage. However, excess NO also halts embryo development, possibly through the production of free radicals. We hypothesize that multiple NOS isoforms are expressed in order to ensure normal preimplantation embryo development and that, in this process, NO acts through the cGMP pathway. Using reverse transcription-polymerase chain reaction, mRNA for all three NOS isoforms was amplified from two-cell, four-cell, morula, and blastocyst embryos. However, blastocyst-stage embryos isolated midmorning on Day 4 of pregnancy expressed only nNOS and eNOS, whereas those isolated midafternoon again expressed all three NOS isoforms. Culture of one-cell embryos in various concentrations of Whitten (positive control), S-nitroso-N-acetylpenicillamine (SNP, a NO donor), L-NA, and/or 8-Br-cGMP demonstrated that NO is acting, at least in part, through cGMP in preimplantation embryo development. In addition, we determined that a critical concentration of NO and cGMP is required for normal embryo development and deviations from this concentration lead to developmental arrest and/or apoptosis of the embryo. This data provides support for a requirement of NO in preimplantation embryo development and one mechanism through which it regulates mitotic division in these embryos.
1 Correspondence. FAX: 704 687 3457; ymhuet{at}email.uncc.edu
Copyright © 2003 by the Society for the Study of Reproduction.