Nitric oxide levels and nitric oxide synthase expression in uterine samples from mares susceptible and resistant to persistent breeding-induced endometritis.

The research examines the role of nitric oxide and nitric oxide synthase in broodmares susceptible and resistant to persistent breeding-induced endometritis, a condition affecting fertility. It was found that susceptible mares had higher levels of nitric oxide and greater nitric oxide synthase expression, indicating a potential role of these elements in delayed uterine clearance following insemination.

Introduction

• This research focuses on breeding-induced endometritis (BIE) in broodmares. While normally resolved by 36 hours after insemination, in approximately 10-15% of susceptible mares there is an impairment in uterine contractility between 7 and 19 hours post-exposure, resulting in a reduction in fertility.
• The researchers sought to understand the role of nitric oxide (NO) and nitric oxide synthase (NOS) in both susceptible and resistant mares.

Methods

• The research involved comparing levels of NO in uterine secretions, and the expression of NOS in uterine biopsies, between susceptible and resistant mares.
• The comparison was conducted 13 hours after insemination.

Results

• The results revealed that mares susceptible to BIE had higher levels of NO in their uterine secretions and a greater expression of NOS in their uterine biopsies compared to resistant mares.

Conclusions

• NO is known to mediate smooth muscle relaxation, but its specific role in persistent BIE has not been previously determined.
• Based on the observed correlation between higher NO levels, greater NOS expression, and BIE susceptibility, the study suggests a role of NO, either directly or within an NO-associated pathway, in delayed uterine clearance following insemination.
• This conclusion, if further supported by research, could potentially open the door to new treatments or preventive measures for BIE in susceptible mares, helping to improve fertility rates.