Chicken and Turkey Spermatozoal Superoxide Dismutase: A Comparative Study1

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Abstract
Superoxide dismutase (SOD) is one of several enzymes in aerobic cells which scavenge for toxic derivatives of oxygen. These derivatives cause lipid peroxidation, a type of cellular damage that may in part explain the loss of fertilizing capability of chicken and turkey spermatozoa stored in vitro. The objective of the present research was to extract SOD from chicken and turkey erythrocytes and spermatozoa and to compare SOD activities between the two types of spermatozoa and between the spermatozoa and isogeneric erythrocytes, cells rich in SOD. Based upon activity of purified extracts, chicken spermatozoa contained 1.48 ± 0.08, while turkey spermatozoa contained 0.32 ± 0.01 activity units/109 cells. Chicken and turkey erythrocytes had 2.65 ± 0.20 and 2.95 ± 0.39 units/109 cells, respectively. When SOD activity was expressed as density, i.e., units/mm3 of cell volume, chicken spermatozoa had an activity density of 10.6 × 10−2 units/mm3, 4.6 times more than turkey spermatozoa, which had 2.3 × 10−2 units/ mm3. The activity density for erythrocytes from both species was ∿2.0 × 10−2 units/mm3. On the basis of cyanide inhibition, erythrocytes contained only cupro-zinc SOD, but spermatozoa contained both cupro-zinc and mangano superoxide dismutases. The lower SOD activity in turkey spermatozoa may result in a greater susceptibility to oxygen toxicity for turkey semen stored in vitro.