Dexamethasone acutely regulates endocrine parameters in stallions and subsequently affects gene expression in testicular germ cells.

The study investigates the impact of the synthetic glucocorticoid dexamethasone on the endocrine system of stallions, as well as on the gene expression within their testicular germ cells. The researchers found that dexamethasone significantly reduced the concentrations of cortisol and testosterone in the stallions, and negatively affected the levels of specific genes related to male fertility.

Objectives and Methods

• The research aimed to probe the effects of glucocorticoids, stress-related hormones known to negatively affect steroidogenesis and spermatogenesis, on stallions. Dexamethasone, a synthetic glucocorticoid, was administered to stallions to examine its impact.
• The study involved administering a therapeutic dose of dexamethasone to three stallions, while three others were given a saline-injection control. The dexamethasone was delivered via two intravenous injections 24h apart.

Results

• Dexamethasone was found to decrease the circulating concentrations of cortisol, an important steroid hormone, by 50% after 24 hours of the initial injection.
• Moreover, dexamethasone also significantly reduced serum testosterone levels by up to 94% between 4 to 20 hours following the initial injection. Despite this, the semen parameters of the treated stallions remained unchanged for the following two weeks.
• In a post-treatment investigation of the stallions’ testes, the researchers discovered that dexamethasone reduced the concentrations of certain gene products, heat shock protein DNAJC4 and sperm-specific calcium channel CATSPER1, by over 60%.

Significance of Findings

• Both the DNAJC4 and CATSPER1 genes are expressed in germ cells during spermiogenesis and have been linked to male fertility in various species, including humans.
• This study is the first to report a decline in the concentrations of DNAJC4 and CATSPER1 mRNA in testes following dexamethasone treatment. The findings suggest that the levels of these mRNAs in sperm may serve as new fertility markers in stallions.