Effect of extracellular adenosine 5 - triphosphate (ATPe) on cryopreserved epididymal cat sperm intracellular ATP concentration, sperm quality and <I>in vitro</I> fertilizing ability

Abstract

Intracellular adenosine 5 - triphosphate (ATP) is essential for supporting sperm function in the fertilization process. During cryopreservation, damage of sperm mitochondrial membrane usually leads to compromised production of intracellular ATP. Recently, extracellular ATP (ATPe) was introduced as a potent activator of sperm motility and fertilizing ability. This study aimed to evaluate; 1) levels of intracellular ATP in frozen-thawed epididymal cat sperm after incubation with extracellular ATP (ATPe) and 2) effects of ATPe on epididymal cat sperm parameters after freezing and thawing. Eighteen male cats were included. For each replicate epididymal sperm from two cats were pooled to one sample (n=9). Each pooled sample was cryopreserved with Tris egg-yolk extender into three straws. After thawing, the first and second straw was incubated with 0, 1.0 or 2.5 mM ATPe for 10 min and evaluated for sperm quality at 10 min, 1, 3 and 6 h post-thawed, and fertilizing ability, respectively. The third straw was evaluated for intracellular ATP concentration in control and with 2.5 mM ATPe treatment. Higher concentration of intracellular sperm ATP was observed in the samples treated with 2.5 mM ATPe compared to the controls (0.339 ± 0.06 µg/2x106 sperm vs 0.002 ±0.003 µg/2x106 sperm, P = 0.05). In addition, incubation with 2.5 mM ATPe for 10 min promoted sperm motility (56.7 ± 5.0 vs 53.3 ± 4.4%, P = 0.05) and progressive motility (3.1 ± 0.2 vs 2.8 ± 0.4, P = 0.05), mitochondrial membrane potential (36.4 ± 5.5 vs 28.7 ± 4.8%, P = 0.05) as well as blastocyst rate (36.1 ±7.0 and 28.8 ±7.4%, P = 0.05) compared to the controls.. In contrast, ATPe remarkably interfered acrosome integrity after 6 h post-thawed incubation. In sum, the present finding in optimal incubation time of post-thaw epididymal cat sperm under proper ATPe condition might constitute a rationale for the other endangered wild felids studies regarding to sperm quality and embryo development.