Cryopreservation of Atlantic salmon Salmo salar sperm: effects on sperm physiology

Resumen:
The objective of this study was to determine the effect of freezing on the function in Atlantic salmon Salmo salar spermatozoa. The semen was frozen in Cortland's medium+1.3M dimethyl sulphoxide+0.3M glucose+2% bovine serum albumin (final concentration) in a ratio of 1:3 (semen:cryoprotectant) as the treatment (T) and fresh semen as the control (F). Straws of 05ml of sperm suspension were frozen in 4cm of N2L. They were thawed in a thermoregulated bath (40 degrees C). After thawing, the percentage of spermatozoa with fragmented DNA [transferase dUTP (deoxyuridine triphosphate) nick-end labelling (TUNEL)], plasma membrane integrity (SYBR-14/PI) and mitochondrial membrane potential (MMit, JC-1) were evaluated by flow cytometry and motility was evaluated by optical microscope under stroboscopic light. The fertilization rates of the control and treatment semen were tested at a sperm density of 15x10(7) spermatozoa oocyte(-1), by observation of the first cleavages after 16h incubation at 10 degrees C. In the cryopreserved semen (T), the mean +/- s.d. DNA fragmentation was 48 +/- 25%; plasma membrane integrity 752 +/- 63%; mitochondrial membrane potential 517 +/- 36%; motility 585 +/- 53%; curved line velocity (V-CL) 612 +/- 174 mu ms(-1); average-path velocity (V-AP) 501 +/- 173 mu ms(-1); straight-line velocity (V-SL) 591 +/- 184 mu ms(-1); fertilization rate 816 +/- 19%. There were significant differences in the plasma membrane integrity, mitochondrial membrane potential, motility, fertilization rate, V-CL, V-AP and V-SL compared with the controls (P<005). Also the mitochondrial membrane potential correlated with motility, fertilization rate, V-CL and V-SL (r=075; r=059; r=077 and r=079, respectively; P<005); and the fertilization rate correlated with V-CL and V-SL (r=059 and r=055, respectively).

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