Abstract
Seminal plasma (SP) of donkey stallions was evaluated using various oxidative stress parameters as well as protease and protease inhibitor activities. SP was obtained by nine donkey stallions. In addition, one donkey stallion with non-obstructive azoospermia was enrolled in this study. Free radical scavenging activity (FRSA), the ferric reducing ability of plasma (FRAP), total antioxidant capacity (TAC), and total thiol level (TTL) were highly correlated with each other and with the protease inhibitor activity. However, only FRAP, TAC, and the nitrate/nitrite concentration (NOx) were significantly correlated with sperm concentration, production, and kinetics. Protease inhibitor activity was highly correlated with sperm concentration and production; however, it did not correlate with sperm kinetics. The azoospermic stallion produced a lower amount of semen than the normospermic stallions and its SP showed a lower antioxidant activity when evaluated with FRAP, TAC, and TTL as well as a higher NOx and a lower protease inhibitor activity. In conclusion, the evaluation of SP oxidative profile by FRAP, TAC, and NOx may provide reliable information on donkey sperm quality whereas protease inhibitor activity may play a role as a marker of the sperm concentration in this species.
Highlights
Once produced in the testicle, the spermatozoa are conveyed along the male genital tract within a modified ultrafiltrate of the blood
Considering the availability of only one azoospermic stallion, it was not possible to perform any statistical comparison. Several differences discriminated this azoospermic individual from normospermic stallions concerning the various methodologies used to evaluate the Seminal plasma (SP) oxidative profile
The azoospermic stallion showed lower ferric reducing ability of plasma (FRAP) (83.9 ± 28.5 vs. 537.1 ± 184.0), Free radical scavenging activity (FRSA) (5.7 ± 2.4 vs. 22.6 ± 14.4), and total thiol levels (TTL) (53.4 ± 2.2 vs. 114.4 ± 36.8) values; vice versa, N Ox values were higher in azoo- than normo-spermic stallions (621.9 ± 7.7 vs. 216.7 ± 120.8)
Summary
Once produced in the testicle, the spermatozoa are conveyed along the male genital tract within a modified ultrafiltrate of the blood. In the female genital tract, SP functions to (i) provide an alkaline environment, thanks to basic polyamines, such as spermine, spermidine, and putrescine, that is useful to counteract the uterine acid environment[10]; (ii) hasten o vulation[11]; (iii) increase blood flow to the uterus and o viducts[12]; (iv) modulate the immune system as reducing the duration of the breeding-induced endometritis through suppressive effects on complement activation, polymorphonucleate (PMN)-chemotaxis, and phagocytosis[9] Besides these positive functions, a recent study in donkey demonstrated a role of fresh and frozen SP in the occurrence of neutrophil extracellular traps (NETs) that are involved in the uterine immune defense against either infectious agents or spermatozoa with potential adverse effects on reproductive function[13]. Having identified an azoospermic individual within the group of animals trained for semen collection, it seemed interesting to compare the oxidative profile and the proteolytic regulatory potential of this individual with the rest of the normospermic group
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