ABSTRACT
Transferrins are a superfamily of iron-binding proteins and are recognized as multifunctional proteins. In the present study, transcriptomic and proteomic methods were used to identify transferrins in the reproductive organs and sperm of out-of-spawning and spermiating sterlet (Acipenser ruthenus) males. The results showed that seven transferrin transcripts were identified in the transcriptome of sterlet, and these transcripts were qualified as two different transferrin genes, serotransferrin and melanotransferrin, with several isoforms present for serotransferrin. The relative abundance of serotransferrin isoforms was higher in the kidneys and Wolffian ducts in the spermiating males compared to out-of-spawning males. In addition, transferrin was immunodetected in sterlet seminal plasma, but not in sterlet spermatozoa extract. Mass spectrometry identification of transferrin in seminal plasma but not in spermatozoa corroborates immunodetection. The identification of transferrin in the reproductive organs and seminal plasma of sterlet in this study provides the potential function of transferrin during sturgeon male reproduction.
ABSTRACT
The loss of sperm quality in sterlet (Acipenser ruthenus) due to freeze-thaw process in cryopreservation was investigated in the present study. Two antifreeze proteins (AFPI or AFPIII) were used at different concentrations of 0.1, 1, 10, and 100 µg/mL. We compared motility, curvilinear velocity, and plasma membrane integrity of fresh, cryopreserved sperm, and sperm cryopreserved in the presence of antifreeze proteins. Fresh sperm (control) had 85 ± 4% motility and 160 ± 2 µm/s curvilinear velocity, respectively. After cryopreservation, the motility of frozen-thawed sperm without addition of antifreeze proteins significantly decreased (44 ± 9%), compared to the control. The highest motility of frozen-thawed sperm was obtained in cryopreserved sperm with addition of 1 µg/mL of AFPIII (58 ± 14%). No significant differences were observed in curvilinear velocity between fresh sperm and cryopreserved sperm with/without addition of AFPI or AFPIII. The flow cytometry analysis revealed that fresh sperm contained 94.5 ± 6% live cells, while the cryopreserved sperm only contained 26.6 ± 14% live cells. Supplementation of antifreeze proteins has significantly improved the percentage of live cells in frozen-thawed sperm, except 0.1 µg/ml of AFPI group. No significant difference in percentage of live cells was detected in the sperm cryopreserved with 10 µg/mL of AFPI or AFPIII, compared to fresh sperm. Thus, addition of antifreeze proteins to cryopreservation medium could be considered to improve the post-thawed sperm quality of sterlet.
