Related Experiment Videos
Abnormal estrous cyclicity after disruption of endothelial and inducible nitric oxide synthase in mice
A Jablonka-Shariff1, S Ravi, A N Beltsos
1Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Abstract:
The roles of nitric oxide (NO) and nitric oxide synthase (NOS) in reproduction were studied by examining the estrous cycle of wild-type (WT) mice, inducible NOS (iNOS)-, and endothelial NOS (eNOS)-knockout mice. We observed an average estrous cycle of 4.8 +/- 0.2 days in WT mice. While we observed no significant influence of iNOS deficiency on cycle length, eNOS-knockout females showed a significantly longer estrous cycle (6.6 +/- 0.6 days; p < 0.03) than WT females, due to an extension of diestrus (p < 0.03). There was no influence of iNOS deficiency on ovulation rate compared with that in WT females; however, eNOS-knockout mice showed a significant reduction (p < 0.05) in ovulatory efficiency relative to WT or iNOS-knockout females. In contrast to WT females, in which the highest level of estradiol (E2) was observed at 1500 h of proestrus, iNOS-knockout females reached a peak of E2 at 1830 h of proestrus. In eNOS-knockout females, the peak of E2 occurred at 1830 h, as in iNOS-knockout mice; however, E2 levels were 5-fold and 3-fold higher (p < 0.05) than levels observed in WT and iNOS-knockout females, respectively. There was no effect of genotype on the plasma LH concentrations at proestrus. On the first day of diestrus, eNOS-knockout females showed significantly higher plasma E2 and progesterone levels (p < 0.05) relative to WT and iNOS-knockout females. The dysfunction in cyclicity, ovulation rate, ovarian morphology, and steroidogenesis in eNOS-knockout female mice strongly supports the concept that eNOS/NO plays critical roles in ovulation and follicular development.
Insights
Endothelial NOS (eNOS) plays a critical role in female reproduction. eNOS-knockout mice exhibit disrupted estrous cycles and reduced ovulation efficiency, highlighting eNOS/NO
Area of Science:
- Reproductive biology
- Endocrinology
- Physiology
Background:
- Nitric oxide (NO) and its synthases (NOS) are implicated in reproductive processes.
- Understanding the specific roles of different NOS isoforms, particularly endothelial NOS (eNOS), is crucial for reproductive health.
Purpose of the Study:
- To investigate the distinct roles of inducible NOS (iNOS) and eNOS in regulating the female estrous cycle and ovulation.
- To elucidate the impact of eNOS deficiency on reproductive hormones and ovarian function.
Main Methods:
- Comparative analysis of estrous cycle length and regularity in wild-type (WT), iNOS-knockout, and eNOS-knockout female mice.
- Assessment of ovulation rate and ovulatory efficiency across different genotypes.
- Measurement of plasma estradiol (E2), progesterone, and luteinizing hormone (LH) levels at specific stages of the estrous cycle.
Main Results:
- eNOS-knockout mice displayed significantly longer estrous cycles and extended diestrus phases compared to WT mice.
- Ovulatory efficiency was significantly reduced in eNOS-knockout females, with no effect observed in iNOS-knockout mice.
- eNOS-knockout females exhibited altered estradiol peak timing and significantly elevated estradiol and progesterone levels during diestrus.
Conclusions:
- Endothelial NOS (eNOS) is essential for normal estrous cyclicity and efficient ovulation in female mice.
- eNOS deficiency leads to reproductive dysfunction, including impaired ovulation and altered steroidogenesis.
- These findings underscore the critical role of the eNOS/NO pathway in regulating key reproductive events such as ovulation and follicular development.