Aging of stallion spermatozoa stored in vitro is delayed at 22°C using a 67 mm glucose-10 mm pyruvate-based media

Background: Most commerce of equine seminal doses is carried out using commercial extenders under refrigeration at 5 degrees C.Objectives: To determine if 10 mM pyruvate in a 67 mM glucose extender and storage at 22 degrees C could be the basis of an alternative storage method to cooling to 5 degrees C.Material and methods: Stallion ejaculates were extendedin: INRA96 (67 mM glucose, non-pyruvate control), modified Tyrode's (67 mM glucose-10 mM pyruvate), supplemented with 0, 10, 50, and 100 mu M itaconate. As itaconate was vehiculated in DMSO, a control vehicle was also included. Sperm motility, viability, mitochondrial membrane potential, and production of reactive oxygen species were measured after collection and again after 48 and 96 h of storage at 22 degrees C. To disclose molecular metabolic changes, spermatozoa were incubated up to 3 h in modified Tyrode's 67 mM glucose-10 mM pyruvate and modified Tyrode's 67 mM glucose, and metabolic analysis conducted.Results: After 96 h of storage aliquots stored in the control, INRA96 had a very poor total motility of 5.6% +/- 2.3%, while in the 67 mM glucose-10 mM pyruvate/10 mu M itaconate extender, total motility was 34.7% +/- 3.8% (p = 0.0066). After 96 h, viability was better in most pyruvate-based media, and the mitochondrial membrane potential in spermatozoa extended in INRA96 was relatively lower (p < 0.0001). Metabolomics revealed that in the spermatozoa incubated in the high pyruvate media, there was an increase in the relative amounts of NAD(+), pyruvate, lactate, and ATP.Discussion and conclusions: Aliquots stored in a 67 mM glucose-10 mM pyruvatebased medium supplemented with 10 mu M itaconate, maintained a 35% total motility after 96 h of storage at 22 degrees C, which is considered the minimum acceptable motility for commercialization. Improvements may be related to the conversion of pyruvate to lactate and regeneration of NAD(+).

Automated summary

This study investigated the effect of adding pyruvate to glucose extender and storing the seminal doses at 22 degrees C instead of the usual 5 degrees C. The results showed that pyruvate-based media with the addition of itaconate at an appropriate concentration could maintain the motility of sperm samples after 96 hours of storage, which is important for commercialization.