Embryonic production of nitric oxide and its role in implantation: a pilot study.
OBJECTIVE
To investigate the ability of human embryos to produce nitric oxide (NO) and correlate its production with embryo quality and pregnancy rate.


METHODS
Twenty-three women participated in the study and were submitted to controlled ovarian stimulation and intracytoplasmic sperm injection. Embryos were singularly cultured in medium microdrops of 50 microL and were replaced, by transcervical transfer, at the 2- to 6-cell stage. In the culture media of each embryo the NO production was assessed by monitoring the levels of its stable oxidation products (nitrites/nitrates).


RESULTS
All the 23 patients underwent embryo transfer. After microinjection 64 embryos were obtained. The mean number of transferred embryos was 2.61 +/- 0.46 and the pregnancy rate was 26%. The mean nitrite/nitrate concentrations of culture medium of each embryo was significantly higher (5.88 +/- 2.34 micromol/L) than in pure P-1 medium (0.81 +/- 0.21 micromol/L; p < 0.001) demonstrating an embryonic secretion of NO. Comparing pregnant (7.34 +/- 2.72 micromol/L) versus nonpregnant patients (5.53 +/- 1.49 micromol/L; p = 0.022), the mean nitrite/nitrate concentrations were significantly higher. Furthermore, the best quality embryos of pregnant women produced significantly higher nitrite/nitrate concentrations than those of not pregnant patients.


CONCLUSIONS
It seems that NO production in nidating embryos is increased and that it may be primarily associated with a better morphology and a better growth potential of developing embryos.
Battaglia
C
C
III Department of Obstetrics and Gynecology, Alma Mater Studiorum--University of Bologna, Via Massarenti, 13, 40138 Bologna, Italy. battaglia@med.unibo.it
Ciotti
P
P
Notarangelo
L
L
Fratto
R
R
Facchinetti
F
F
de Aloysio
D
D
D000328:Adult; D003470:Culture Media; D010064:Embryo Implantation; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008297:Male; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D009573:Nitrites / Q000378:metabolism; D010062:Ovulation Induction; D010865:Pilot Projects; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D020554:Sperm Injections, Intracytoplasmic
D003470:Culture Media; D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide