Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of rainbow trout (Oncorhynchus mykiss) seminal plasma proteins and their correlation with semen characteristics.

Background: Fish seminal plasma is a complex mixture made of different components. In few studies on some fish species such as rainbow trout, Nile tilapia and jundia fish (Rhamdia quelen) characterization of seminal plasma proteins were shown. Meanwhile there is little information regarding the correlation between specific seminal proteins and semen characteristics in rainbow trout. The objective of the present study was to evaluate the seminal plasma protein profiles and their relation with some semen characteristics in rainbow trout. Materials, Methods & Results: Nine mature male rainbow trout with total weight 2300 +/- 200 g were used. A total of nine male fish were anaesthetized by clove oil bath (50 mu l L-1) and semen was collected by abdominal massage. Semen variables (spermatocrit, concentration, duration of activity, percent of motility, total protein) were recorded. Seminal plasma was also separated by centrifugation and subjected to SDS-PAGE analysis. Gel images were analysed to determine molecular weight and relative protein content (pixel density) using the Total Lab TL120 computer program. Spermatocrit (%), sperm concentration (cell mL(-1)), duration of sperm activity (sec), percentage of sperm motility and total protein (mg dL(-1)) were 22.67, 12.35 x 10(9), 36.56, 89.33 and 81.49 respectively. Nine protein bands were identified on the 15% gel ranging from 11.74 to 68.12 kDa which seven were present in all samples. Band 1 (68.12 kDa), 2 (60.20 kDa) and 3 (54.19 kDa) were prominent (56.92% of the bands) in semen samples. Sperm concentration was negatively correlated with band 1 (68.12 kDa), 2 (60.20 kDa), 7 (32.72 k Da) and 8 (20.96). Percent of sperm motility showed positive correlation with band 3 (54.19 kDa) and 9 (11.74). Negative correlation was also revealed between spermatocrit and band 7 (32.72 k Da). Discussion: In the present study, spermatocrit (%) and duration of sperm activity (sec) were 22.67 and 36.56. In our study values for sperm concentration (cell mL-1) and percentage of spem motility were 12.35 x 10(9) and 89.33 while in previously study these values were 7.89 x 10(9) and 88.5. Nine bands with molecular weights ranging from 11.74 to 68.12 kDa were detected in this study. The proteins with molecular weight higher than 54 kDa were prominent (56.92% of the bands). In the current study protein bands 3 (54.19 kDa) and 9 (11.74 kDa) were positively correlated with percent of sperm motility. It can be concluded that protein band 3 (54.19) and 9 (11.74) may modulate sperm function by providing energy and protection for spermatozoa as a complementary substance. Also According to our results, protein bands 1 (68.12), 2 (60.20), 7 (32.72) and 9 (11.74) negatively correlated with sperm concentration. It seems that these protein fractions could relate to other parameters in rainbow trout semen which are detrimental to sperm cells. On the other hand, all protein bands showed no correlation with other spermatological parameters such as total protein and duration of sperm activity. In conclusion, the present study shows that there is a correlation between some of the seminal plasma protein fraction and semen characteristics.