In the present study, the increased testosterone levels in both blood and seminal plasma of the infertile compared with control fertile male camels, suggests that infertile camels could have primary defects in the spermatogenesis process (Babu et al. 2004; Ali et al. 2018). Other possible explanation for this elevated testosterone levels could be due to the increased density of the interstitial cells on the expense of the seminiferous tubules (Ali et al. 2018). Moreover, changes in the structure and function of Leydig cells accompanying seminiferous tubule damage could explain the rise in blood plasma testosterone concentrations of infertile camels (Tibary, 2004; Ali et al. 2014) which is reflected in the seminal plasma. The high blood testosterone levels may also be related to a rise in LH levels that causes androgen resistance in the infertile dromedary male camels (Fraietta et al. 2013). Contradictory to the previous findings, Waheed et al. (2015) reported a higher testosterone concentration in the serum blood of fertile compared to infertile male dromedary camels. Previous studies suggested that male infertility can be caused by a variety of conditions; such as gonadotropin deficiency (Babu et al. 2004), primary testicular failure (Ali et al. 2014), spermatogenic failure (Bhasin et al. 2007), or androgen resistance (Fraietta et al. 2013). Furthermore, in the present study, significant rises in seminal plasma testosterone levels of infertile camels support the suggestion that those animals could be showing a status of spermatogenic failure, and/or androgen resistance conditions. Thus, testosterone in both seminal plasma and blood of dromedary camels could be used as fertility-associated biomarkers (Waheed et al. 2015).
In the current study, no difference was observed in aldosterone levels in the blood or seminal plasma among both groups. However, aldosterone levels are slightly altered by dehydration in dromedary camels (Ali et al. 2012). Also, aldosterone is the chief regulator of sodium, potassium, and chloride metabolism, thus controlling the body's water and electrolyte balances (Yang and Ma, 2009). Accordingly, the detected aldosterone level in the present study suggested that both fertile and infertile camel males had similar environmental conditions regarding dehydration and water balances. Also, the equal response in circulating aldosterone levels in both groups can be explained by the equal amount of sodium in the serum and presumed osmolality in plasma, though unmeasured. In addition, the current results confirmed a positive association between blood plasma testosterone and aldosterone in infertile camels. Inversely, in vivo and in vitro experiments in male rats (Kau et al. 1999), suggested that testosterone inhibits the basal and Ang II- and corticotropin (ACTH)-stimulated release of aldosterone. This mechanism occurs via inhibition of aldosterone synthase activity and cytochrome P-450 side-chain cleavage (P450scc) activity, and ACTH-stimulated c-AMP accumulation in the zona glomerulosa cells. Also, endogenous androgens (testosterone) exert anti-hypertensive effects that appear to involve non-genomic and possibly genomic mechanism(s), resulting in reductions in RAS expression in the kidney and enhanced systemic vasodilation in male rats (Hanson et al. 2020). Instead, the present study indicated a negative association between blood aldosterone and seminal plasma testosterone in infertile camels.
According to the current findings, there was a significant difference in the motility, viability, concentration, and abnormalities of sperm and the fertility status between the control and infertile male camels. Similar data were reported previously in dromedary camels (Mostafa et al. 2014, Waheed et al. 2015; Waheed et al. 2018). Several factors can contribute to poor semen quality, including impaired spermatogenesis, endocrine malfunctions, alteration of the microenvironment of seminiferous tubules, and accessory gland infections (Robaire and Hamzeh, 2011). Also, it has been reported that testicular hypoplasia is an inherited trait in the dromedary camels, characterized by the absence of or the atretic seminiferous tubules of the testicular parenchyma resulting in spermatogenic failures (Tibary, 2004; Ali et al. 2014). Furthermore, decreased sperm motility and concentration, as well as increased abnormalities, were associated with higher iron (Fe), zinc (Zn), and copper (Cu) concentrations in serum and seminal plasma of infertile camels (Waheed et al. 2018). Besides, higher levels of arsenic (As), cadmium (Cd), and lead (Pb) in seminal plasma and blood were associated with lower levels of semen quality variables and infertility in dromedary camels (Meligy et al. 2019). Likewise, the present study showed a negative association between blood plasma aldosterone and sperm motility in control camels. Also, a positive relationship was indicated between seminal plasma aldosterone and sperm abnormality in the infertile camels. A possible link between aldosterone and semen quality is the local RAS regulator of seminal plasma electrolytes, steroidogenesis, and spermatogenesis, as well as sperm function (Gianzo and Subirá, 2020). Also, the RAS acts locally through different paracrine and autocrine mechanisms (Gianzo and Subirá, 2020). Yet, the definitive explanation for aldosterone's influence on the semen quality of the dromedary camel still needs to be resolved.