Erythrocyte and spermatozoa glucose-6-phosphate dehydrogenase activity in merino rams: An experimental study

Background: Glucose-6-phosphate dehydrogenase (G6PD) is the first enzyme of the pentose phosphate metabolic pathway that supplies reducing agents by maintaining the level of reduced nicotinamide adenine dinucleotide phosphate.
Objective: It was aimed to determine the activity of erythrocyte and spermatozoa G6PD in the breeding and non-breeding seasons in Merino rams. And also, to find out the relation of these parameters with sperm quality parameters for better understanding the role of this enzyme in male fertility.
Materials and Methods: 1.5-2 yr-old healthy, 14 Merino rams were involved. Ejaculate samples were collected using an artificial vagina, in October (the breeding season) and April (the non-breeding season). Blood samples were collected prior to sperm collection. Sperm volume (ml), motility (%), mass activity (1-5), concentration (×10⁶), viability (%), abnormal acrosome morphology (%) and abnormal sperm morphology (%) was evaluated. The activities of spermatozoa and erythrocyte G6PD were determined and the relation of sperm parameters with G6PD activity was evaluated.
Results: Erythrocyte G6PD activity was higher (p≤0.001), whereas spermatozoa G6PD activity was lower (p≤0.001) in the breeding season (1.928±0.231 U/g hemoglobin, 129.65±28.41 U/g protein, respectively) from that in the non-breeding (0.530±0.066 U/g hemoglobin, 562.36±94.92 U/g protein, respectively). There were also significant differences among sperm quality parameters within the seasons. Positive correlation was determined between spermatozoa G6PD activity (r=0.053, p=0.03 and sperm concentration in the breeding season.
Conclusion: Higher spermatozoa G6PD activity in October, where the level of polyunsaturated fatty acids is suggested to be increased, may reflect the increased need of nicotinamide adenine dinucleotide phosphate and thus higher G6PD activity for the oxidative balance.