Effects of relaxin and IGF-I on capacitation, acrosome reaction, cholesterol efflux and utilization of labeled and unlabeled glucose in porcine spermatozoa

Association between levels of insulin-like growth factor-1 in serum and seminal plasma with fresh and frozen-thawed semen characteristics in Beetal bucks

The aim of this study was to investigate the relationship between the levels of insulin-like growth factor-1 (IGF-1) in serum and seminal plasma and the characteristics of semen in Beetal bucks (Capra hircus). A total of 12 adult Beetal bucks were involved in the study, with each buck providing six ejaculates collected using a standard artificial vagina (n = 72 total). Only qualified semen samples (volume of 0.7 mL, a mass motility rating of 3+ or higher on a 0-+ scale, and individual progressive motility of 80% or more) divided into three fractions were processed for estimation of IGF-1 and other seminal parameters like motility, viability, acrosome integrity, sperm abnormality and superoxide dismutase (SOD) activity. The first and second fraction were diluted and extended with Optixcell extender (1:15 ratio). The first ejaculate fraction was processed for studying fresh semen parameters and the second fraction was cryopreserved for evaluating frozen semen parameters. French mini straws (0.25 mL) were used for semen filling, and polyvinyl alcohol powder of different colours was used for sealing the extended semen. The third fraction of each ejaculate was centrifuged at room temperature (1100 × g for 7 min) to separate the seminal plasma. Additionally, blood samples were taken from each buck on the same day as semen collection, resulting in a total of 36 blood samples. The results revealed a significant positive correlation (r = .4243; p < .05) between the concentration of IGF-1 in both serum and seminal plasma of the Beetal bucks. Furthermore, the concentration of IGF-1 in serum showed significant positive correlations with sperm viability (r = .554; p < .05), acrosome integrity (r = .527; p < .05), post-thaw sperm motility (r = .407; p < .01), post-thaw sperm viability (r = .426; p < .01) and post-thaw acrosome integrity (r = .333; p < .05). However, it had a significant negative correlation with SOD activity in fresh semen (r = -0.458; p < .01). Moreover, the concentration of IGF-1 in seminal plasma demonstrated significant positive correlations with individual progressive motility (r = .341; p < .05), sperm viability (r = .527; p < .05), acrosome integrity (r = .539; p < .05), sperm plasma membrane integrity (r = .464; p < .05), post-thaw sperm motility (r = .644; p < .01), post-thaw sperm viability (r = .643; p < .01), post-thaw acrosome integrity (r = .487; p < .01) and post-thaw sperm plasma membrane integrity (r = .521; p < .01). Additionally, it showed a significant negative correlation with SOD activity in both fresh semen (r = -0.714; p < .01) and frozen semen (r = -0.558; p < .01) of Beetal bucks. Based on these findings, IGF-1 in seminal plasma can be considered as a potential biomarker for the selection of bucks for breeding purposes.

Relaxin (a regulatory-peptide) enhances cryotolerance, fertility potential and plasma reproductive hormones of Nili Ravi buffalo (Bubalus bubalis) during low breeding season

This study investigated the beneficial effects of relaxin on cryotolerance of buffalo spermatozoa and reproductive hormones during low breeding season. Collected semen was diluted in five aliquots with relaxin addition (0.25 mg/mL, 0.50 mg/mL, 0.75 mg/mL, 1 mg/mL, and control). After gentle dilution (37°C), cooling (4°C, 2 h), equilibration (4°C, 4 h), and packaging (straws, polyvinyl French, 0.5 mL), frozen (cell freezer), and thawed (37°C, 30 s) for analysis. Blood samples were collected at different time intervals i.e., -60, -30 and 0 min (pre-dose) and 30, 60, 90, 120 and 150 min (post-dose) from a jugular vein. This study manifest that adding relaxin (1 mg/ mL) in freezing medium ameliorates sperm motility, functionality (%), and seminal plasma total antioxidant capacity (TAC, μM/L) than control during low breeding season. Furthermore, we found that relaxin supplementation at 1 mg/mL significantly improves seminal plasma ATP concentrations (nmol/million) than control, 0.25 mg/mL, and 0.50 mg/mL, and fertility (control, and 0.75 mg/mL). Further, relaxin injection significantly improves plasma T, LH and IGF-1 levels (150 and 120 min vs. -60, and - 30), and FSH, KP, and GnRH concentrations (150 min vs. -60), during low breeding season. Taken together, this study revealed that relaxin ameliorates motility, functionality, and fertility of buffalo spermatozoa. Moreover, relaxin injection (1 mg/mL) improves essential reproductive hormones levels in buffalo signifying its importance in the field of reproductive physiology. Further studies are required to determine the exact mechanism of action of relaxin in enhancing semen quality, fertility and reproductive hormones.

Fertility-associated biochemical components in seminal plasma and serum of buffalo (Bubalus bubalis) bulls

The present study looks for components in seminal plasma (SP) and/or serum that are closely related to in vivo fertility of buffalo bulls. Fourteen healthy mature buffalo bulls were classified according to their in vivo fertility into fertile (n = 10) and subfertile (n = 4) groups. Semen and serum samples were collected from all animals for 12 replicates. The collected ejaculates were examined for sperm characteristics before being centrifuged to collect SP for hormonal (FSH, LH, testosterone, and IGF-1), biochemical [total antioxidant capacity (TAC), catalase (CAT), glutathione peroxidase (GPx), nitric oxide (NO), malondialdehyde (MDA), fructose, total protein, albumin, triglycerides, cholesterol, and high-density lipoprotein (HDL)] and proteomic (SDS-PAGE) analyses. Likewise, serum levels of FSH, LH, testosterone, IGF-1, glucose, total protein, albumin, triglycerides, cholesterol, and HDL were determined. All sperm characteristics and the majority of sperm kinematics were (P < 0.01) different between fertile and subfertile groups. Seminal and serum levels of FSH, LH, testosterone, and IGF-1 were higher (P < 0.01) in the fertile group, but only seminal fructose, total protein, albumin, triglycerides, cholesterol, and HDL were higher (P < 0.01) in the fertile group. Moreover, the fertile group had greater TAC, CAT, GPx, and NO, but the subfertile group had greater MDA. Protein bands of 14, 15, 26, 30, and 55 kDa were larger and denser in the SP of the fertile group but were smaller and faint to absent in that of the subfertile group. Also, the protein fractions of detected protein bands demonstrated a substantial influence of fertility on those of 16, 26, 30, and 55 kDa. In conclusion, sperm characteristics and kinematics with serum, and/or seminal hormonal and biochemical components, should be evaluated for reliable prediction of buffalo bull fertility. Furthermore, protein bands of 26, 30, and 55 kDa may represent fertility-associated proteins in buffalo bull SP.

Effect of platelet-rich plasma (PRP) on post-thaw quality, kinematics and in vivo fertility of fertile and subfertile buffalo (Bubalus bubalis) spermatozoa

This study investigated the effect of adding platelet-rich plasma (PRP) in semen extender prior cryopreservation on post-thaw quality, kinematics, and in vivo fertility of fertile and subfertile buffalo spermatozoa. Eleven buffalo bulls were classified based on their conception rate (CR) into fertile (n = 8, CR > 55%) and subfertile (n = 3, CR < 35%) groups. Ejaculates were collected with artificial vagina, pooled, and dispensed into 6 aliquots, diluted with Tris-egg yolk-glycerol extender supplemented with different proportions of PRP [0% (control), 5%, 10%, 15%, 20%, and 25%] followed by cryopreservation using standard procedures. Post-thaw sperm quality, kinematics, antioxidant activity, cryosurvival rate, and in vivo fertility were compared between fertile and subfertile groups and among proportions of PRP within each group. The results showed that 15% PRP greatly (P < 0.001) improved sperm characteristics, average path velocity, and curvilinear velocity of the subfertile group. Interestingly, 5%, 10%, and 15% PRP greatly (P < 0.001) reduced malondialdehyde content and improved enzymatic (glutathione peroxidase and superoxide dismutase) and total antioxidant capacity in fertile and subfertile groups. However, these three proportions of PRP significantly (P < 0.001) improved the cryosurvival rate of the subfertile group; only 15% PRP greatly improved CR of subfertile (60.83% vs. 34.17%) animals to be comparable with that of fertile ones treated with 5 (59.17%) and 10% (60.83%) PRP. In conclusion, adding 15% PRP to semen extender before cryopreservation is recommended to improve post-thaw quality, antioxidant activity, and in vivo fertility of buffalo semen particularly of the subfertile animals.

IGF-1 supplementation in semen affects mitochondrial functional and calcium status of buffalo sperm following cryopreservation

This study was designed to examine the effects of seminal insulin-like growth factor-1 (IGF-1) supplementation on structural and functional properties of buffalo sperm post cryopreservation. Semen ejaculates from buffalo bulls (n = 6) were proportioned into four aliquots and diluted with egg yolk-based extender. Prior to equilibration, IGF-1 was added to extender as four treatments: group IGF0 (no supplementation), IGF150 (150 ng/mL), IGF250 (250 ng/mL) and IGF350 (350 ng/mL). The extended semen was transferred into 0.25 mL mini-straws, equilibrated (4 °C at 4 h), and cryopreserved. Total sperm motility was greater (P < 0.05) when there was the IGF150 treatment compared with values for other groups. Furthermore, with the IGF150 treatment there was the least and greatest (P < 0.05) mitochondrial superoxide status and membrane potential, respectively. Similarly, with the IGF150 treatment there was a greater (P < 0.05) sperm membrane integrity with a lesser (P < 0.05) calcium status compared to values for the other groups. In conclusion, seminal IGF-1 supplementation affects the structural and functional properties of buffalo sperm following cryopreservation.

Effect of relaxin on cryopreserved beef bull semen characteristics

This study aimed to improve the quality of cryopreserved beef bull (Piedmontese) semen by incorporation of relaxin in diluted semen before cryopreservation procedures. Semen samples were collected from 4 proven fertile bulls, using artificial vagina, once per week for 8 consecutive weeks and pooled together then diluted with Bullxcell® extender, and supplemented with different concentrations of relaxin (0 (control), 25, 50 and 100 ng/ml) before cooling, equilibration and freezing procedures. Frozen semen was thawed and assessed for motility by Computer-Assisted Sperm Analysis and vitality parameters such as acrosome, plasma membrane and DNA integrities, apoptosis, mitochondrial membrane potential, mucus penetration and SOD activity. The developmental potential of bovine embryos produced in vitro by using relaxin-treated was also investigated. In the present study, 50 and 100 ng/ml relaxin incorporation in extended bull semen before cryopreservation induced a reduction of sperm motility immediately after thawing (0h), whereas, during long incubation periods (1-2 h), relaxin showed a significant positive effect on sperm quality by improving the sperm motility and velocity parameters. Interestingly, sperm vitality was improved by 25 and 100 ng/ml relaxin and the blastocyst developmental rate was significantly increased in the 25 ng/ml relaxin group compared with controls (52/118, 44.0% vs. 32/116, 27.6%, respectively). These findings suggest a potential use of relaxin at the doses tested in the present study as an additive in the cryopreservation media of bull semen to improve sperm quality.

Effect of relaxin on semen quality variables of cryopreserved stallion semen

The aim of the study was to ascertain effects of different concentrations of relaxin added to extender medium during the pre-freezing incubation periods on quality variables of stallion frozen-thawed spermatozoa. Semen samples collected from three stallions were filtered, diluted with skim milk, and centrifuged at 600g for 10 min. Sperm pellets were suspended in BotuCrio freezing medium to a final concentration of 50 × 10⁶ sperm/mL. The diluted semen was divided into five experimental groups supplemented with 0 (control), 12.5, 25, 50, or 100 ng/mL of relaxin. The semen samples were transferred into 0.5 mL straws, equilibrated at 5 °C for 30 min, and placed in liquid nitrogen (LN₂) vapour for 15 min before being plunged into LN₂. After thawing, sperm samples were evaluated for motility and velocity variables, mitochondrial membrane potential, apoptosis, and plasma membrane and DNA integrities. For sperm motility variables, there were dose- and time-dependent effects, with the largest values recorded when 12.5 and 25 ng/mL relaxin were used for 0-120 min of incubation. Furthermore, at all of the concentrations at which there were evaluations, relaxin additions to semen diluent led to a marked improvement in sperm mitochondrial membrane potential and a lesser percentage of apoptotic cells compared to the control group. Plasma membranes and DNA integrities were not affected by relaxin supplementations to the diluent. In conclusion, supplementation of relaxin in extender before semen cryopreservation, especially at 12.5 and 25 ng/mL, had a positive effect on the sperm quality variables.

Across-sex genomic-assisted genetic correlations for sex-influenced traits in Brahman cattle

Background

This study aimed at estimating genetic parameters of sex-influenced production traits, evaluating the impact of genotype-by-sex interaction, and identifying the selection criteria that could be included in multiple-trait genetic evaluation to increase the rate of genetic improvement in both sexes. To achieve this goal, we used 10 male and 10 female phenotypes, which were measured in a population of 2111 Australian Brahman cattle genotyped at high-density.

Results

Heritability estimates ranged from very low (0.03 ± 0.03 for cows’ days to calving at first calving opportunity, DC1), to moderate (0.33 ± 0.08 for cows’ adult body weight, AWTc), and to high (0.95 ± 0.07 for cows’ hip height, HHc). Genetic correlation (r_g) estimates between male and female homologous traits were favorable and ranged from moderate to high values, which indicate that selection for any of the traits in one sex would lead to a correlated response with the equivalent phenotype in the other sex. However, the estimated direct response was greater than the indirect response. Moreover, Pearson correlations between estimated breeding values obtained from each sex separately and from female and male homologous traits combined into a single trait in univariate analysis ranged from 0.74 to 0.99, which indicate that small ranking variation might appear if male and female traits are included as single or separate phenotypes. Genetic correlations between male growth and female reproductive traits were not significant, ranging from − 0.07 ± 0.13 to 0.45 ± 0.65. However, selection to improve HHc and AWTc in cows may reduce the percentage of normal sperm at 24 months of age (PNS24), possibly due to correlated effects in the same traits in males, which are related to late maturing animals.

Conclusions

Hip height in cows and PNS24, as well as blood insulin-like growth factor 1 (IGF1) concentration in bulls at 6 months of age are efficient selection criteria to improve male growth and female reproductive traits, simultaneously. In the presence of genotype-by-sex interactions, selection for traits in each sex results in high rates of genetic improvement, however, for the identification of animals with the highest breeding value, data for males and females may be considered a single trait.

Electronic supplementary material

The online version of this article (10.1186/s12711-019-0482-6) contains supplementary material, which is available to authorized users.

Serum and seminal plasma IGF-1 associations with semen variables and effect of IGF-1 supplementation on semen freezing capacity in buffalo bulls

The objective of the study was to establish correlation of seminal and serum IGF-1 with seminal attributes, estimate antioxidant potential of IGF-1 by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays and to study the effect of IGF-1 supplementation on semen cryopreservation. For this study, buffalo bulls were divided into sub-fertile (n = 2) and normal (n = 5) on the basis of sperm mass motility and individual motility. The serum IGF-1 concentration of normal bulls was greater than in sub-fertile bulls, but there was no difference in the seminal IGF-1 concentration among the groups. The values from correlation analyses indicated that serum IGF-1 concentration is positively correlated with semen mass motility and sperm concentration. In the second experiment, IGF-1 did not have antioxidant activities when assessed with DPPH and FRAP assays. In the third experiment, the ejaculates of normal and sub-fertile bulls were cryopreserved using semen extender in which there was IGF-1 supplementation at 0 (control), 50, 100, 150, 200, 250, 350 and 450 ng/mL of extender. Supplementation of IGF-1 at 250 ng/ml resulted in improved sperm motility, longevity and membrane intactness as compared to control after cryopreservation of semen from normal buffalo bulls, but not sub-fertile bulls. In summary, serum IGF-1 concentration was correlated with sperm mass motility and concentration in buffalo bulls and supplementation of IGF-1 protected sperm during the cryopreservation process but effects were not due to direct antioxidant activity.

Effect of Relaxin on Fertility Parameters of Frozen-Thawed Buffalo (Bubalus bubalis) Sperm

The aim of this work was to evaluate the effect of relaxin on fertility parameters of buffalo frozen/thawed sperm. Sperm were incubated in the absence of capacitating agents (negative control), with a known capacitating agent such as heparin (positive control) and with 50 and 100 ng/ml relaxin for 2 and 4 h. Sperm viability, motility, capacitation and the effect of relaxin on the fertilizing ability after heterologous IVF were evaluated. Although viability was not affected, relaxin increased (p < 0.05) sperm motility compared to the negative and positive controls both after 2 h (60.0 ± 2.0, 60.0 ± 3.1, 68.3 ± 1.7 and 69.4 ± 2.7, respectively, in negative control, positive control, 50 and 100 ng/ml relaxin) and 4 h (55.0 ± 2.5, 53.3 ± 3.0, 62.2 ± 3.0 and 65.0 ± 3.2, respectively, in negative control, positive control, 50 and 100 ng/ml relaxin) incubation. When sperm were incubated with both 100 ng/ml relaxin and heparin, a decrease (p < 0.01) of pattern A, that is low capacitation level, was observed compared to the negative control both after 2 h (54.4, 34.3 and 36.4%, respectively, in negative control, positive control and 100 ng/ml relaxin) and 4 h (51.9, 35.0 and 34.3%, respectively, in negative control, positive control and 100 ng/ml relaxin). Moreover, an increase (p < 0.01) of pattern EA, that is high capacitation level, was recorded with 100 ng/ml relaxin and heparin compared to the negative control both after 2 h (44.1, 59.3 and 57.7%, respectively, in negative control, positive control and 100 ng/ml relaxin) and after 4 h (43.0, 54.4 and 56.0%, respectively, in negative control, positive control and 100 ng/ml relaxin). Finally, relaxin increased (p < 0.01) cleavage rate compared to the negative control (57.1 ± 4.4, 72.5 ± 6.0, 71.4 ± 5.5 and 73.6 ± 2.9, respectively, in negative control, positive control, 50 and 100 ng/ml relaxin). In conclusion, relaxin has a beneficial effect on motility, capacitation and fertilizing ability of frozen-thawed buffalo sperm.

Effect of insulin-like growth factor I on functional parameters of ram cooled-stored spermatozoa

The aim of the study was to examine the effects of insulin-like growth factor I (IGF-I) on ram sperm traits after hypothermic storage. Sperm ejaculates from Lacaune rams were diluted in a Tris extender, pooled, divided into groups of IGF-I doses tested (0, 10, 100 or 200 ng.ml−1) and stored (0–5°C) for 96 h. IGF-I elevated whole sperm motility as measured by a Computer-assisted Sperm Analyser (CASA) system, by 24 h (10 ng.ml−1) and 48 h (200 ng.ml−1) of storage, and by progressive movement on each day of storage. After 72 h the sperm samples were analysed for plasma membrane integrity (peanut agglutinin–fluorescein isothiocyanate), membrane stability (annexin V–Fluos) and apoptosis (Yo-Pro®-1) using fluorescence microscopy. The addition of IGF-I (at 100 or 200 ng.ml−1) reduced the ratio of sperm with disrupted membranes and the ratio of annexin V-labelled sperm. The ratio of apoptotic sperm was reduced by IGF-I given at 10 or 100 ng.ml−1 compared with control. Sperm fertilizing ability, determined at 48 h by an in vitro fertilization (IVF) test on bovine oocytes, was increased by IGF-I given at 100 ng.ml−1 from 47.0 to 67.7%. In conclusion, IGF-I maintained ram sperm functions following cooling storage and its effects were reflected in sperm fertilizing ability in vitro.

Intracellular signaling cascades induced by relaxin in the stimulation of capacitation and acrosome reaction in fresh and frozen-thawed bovine spermatozoa

Relaxin is one of the 6-kDa peptide hormones, which acts as a pleiotropic endocrine and paracrine factor. Our previous studies revealed that sperm capacitating medium containing relaxin induced capacitation and acrosome reaction (AR) in fresh and frozen-thawed porcine or bovine spermatozoa. However, the intracellular signaling cascades involved with capacitation or AR induced by relaxin was unknown. Therefore, the present study was designed to investigate the intracellular signaling cascades involved with capacitation and AR induced by relaxin in fresh and frozen-thawed bovine spermatozoa. Spermatozoa were incubated in sperm Tyrode's albumin lactate pyruvate (Sp-TALP) medium supplemented with (40 ng ml(-1)) or without relaxin, and subjected to evaluation of chlortetracycline staining pattern, cholesterol efflux, Ca(2+)-influx, intracellular cyclic adenosine monophosphate (cAMP) and protein tyrosine phosphorylation. Capacitation and AR were increased (P<0.05) in both fresh and frozen-thawed spermatozoa incubated with relaxin. Cholesterol effluxes were greater in the fresh (P<0.01) and frozen-thawed (P<0.05) spermatozoa incubated with relaxin than the spermatozoa incubated without relaxin. Ca(2+)-influxes were also significantly stimulated by relaxin in the fresh (P<0.01) and frozen-thawed (P<0.05) spermatozoa. The Sp-TALP medium containing relaxin influenced the generation of intracellular cAMP in the fresh (P<0.01) and frozen-thawed (P<0.05) spermatozoa, and exhibited higher exposure of protein tyrosine phosphorylation in both sperm types than the medium devoid of relaxin. Therefore, the results postulate that relaxin exerts the intracellular signaling cascades involved with capacitation and AR through accelerating the cholesterol efflux, Ca(2+)-influx, intracellular cAMP and protein tyrosine phosphorylation in fresh and frozen-thawed bovine spermatozoa.

Effect of selenium and vitamin E on acrosome reaction in porcine spermatozoa

Purpose

Selenium (Se) and vitamin E (Vit-E), as an integral part of antioxidant systems, play an important role in the motility and acrosome reaction (AR) of mammalian spermatozoa. The purpose of this study was to investigate the effect of Se and Vit-E on motility, viability, AR and accumulation of ammonia in the culture medium during different incubation periods in porcine sperm.

Methods

Sperm samples were washed, swum-up and incubated at 37°C for 1 and 3 h in Sp-TALP medium supplemented with sodium selenite (SS), seleon l-methionine (SeMet) and Vit-E in the presence or absence of ammonia. Sperm motility was determined on the basis of movement quality examined by phase microscopy. Viability and AR of spermatozoa were assessed by Hoechst 33258 and chlortetracycline (CTC) staining technique, and accumulation of ammonia was measured by the indophenol method. The incorporation of ¹⁴C(U)-glucose was assessed with a liquid scintillation counter.

Results

In experiment 1, the sperm motility, viability, AR and incorporation of ¹⁴C(U)-glucose increased significantly (P < 0.05) in SS, SeMet and Vit-E (5, 5 μg/l and 1.0 mM, respectively) compared with the control. In experiment 2, treatment of the sperm with SeMet and SeMet + Vit-E in the presence of 300 μM ammonia also resulted in a significant increase (P < 0.05) in the rate of motility, viability, AR and incorporation of ¹⁴C(U)-glucose. In contrast, the accumulation of ammonia was reduced by SeMet and SeMet + Vit-E compared with the other treatments.

Conclusions

These findings indicate that SeMet and SeMet + Vit-E may play an important role in reducing the accumulation of ammonia and subsequently in increasing the rate of AR and the utilization of glucose in porcine spermatozoa.

Metabolism of exogenous fatty acids, fatty acid-mediated cholesterol efflux, PKA and PKC pathways in boar sperm acrosome reaction

Purpose

For understanding the roles of fatty acids on the induction of acrosome reaction which occurs under association of cholesterol efflux and PKA or PKC pathways in boar spermatozoa, metabolic fate of alone and combined radiolabeled ¹⁴C-oleic acid and ³H-linoleic acid incorporated in the sperm was compared, and behavior of cholesterol and effects of PKA and PKC inhibitors upon fatty acid-induced acrosome reaction were examined.

Methods

Semen was collected from a Duroc boar, and the metabolic activities of fatty acids in the spermatozoa were measured using radioactive compounds and thin layer chromatography. Cholesterol efflux was measured with a cholesterol determination assay kit. Participation of fatty acids on the AR through PKA and PKC pathways was evaluated using a specific inhibitor of these enzymes.

Results

Incorporation rate of ¹⁴C-oleic acid into the sperm lipids was significantly higher than that of ³H-linoleic acid (P < 0.05). The oxidation of ¹⁴C-oleic acid was higher in combined radiolabeling rather than in one. The highest amounts of ³H-linoleic acid and ¹⁴C-oleic acid were recovered mainly in the triglycerides and phospholipids fraction, and ¹⁴C-oleic acid distribution was higher than the ³H-linoleic acid in both labeled (P < 0.05) sperm lipids. In the ³H-linoleic and ¹⁴C-oleic acid combined radiolabeling, the incorporation rate of the radioactive fatty acids in all the lipid fractions increased 15 times more than the alone radiolabeling. Boar sperm utilize oleic acid to generate energy for hyperactivation (P < 0.05). Supplementation of arachidonic acid significantly increased (P < 0.05) cholesterol efflux in sperm. When spermatozoa were incubated with PKA or PKC inhibitors, there was a significant reduction of arachidonic acid-induced acrosome reaction (AR) (P < 0.05), and inhibition by PKA inhibitor is stronger than that by PKC inhibitor.

Conclusions

Incorporation of unsaturated fatty acids, especially oleic acid, into triglycerides and phospholipids provides prerequisite energy for AR. Cholesterol efflux by arachidonic acid triggers AR. Arachidonic acid activated PKA and PKC pathway participate in induction of the AR.