, Volume 21, Issue 3, pp 193-200

Maintenance of steelhead trout (Oncorhynchus mykiss) sperm at different in vitro oxygen tensions alters ATP levels and cell functional characteristics

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Abstract

Adenosine triphosphate (ATP) levels in sperm from steelhead trout (Oncorhynchus mykiss) were found to be 12.0 ± 1.4 pmol ATP per 106 sperm cells. Sperm were stored at 0–2 °C for up to 72 h under 100 and 21% O2, and 100% N2. The sperm ATP content of samples maintained under 100 and 21% O2 both decreased to about 70 and 50% of initial values after 24 and 72 h, respectively. ATP levels of sperm stored under 100% N2 decreased to 20% of initial values after only 4 h and to less than 10% of initial values after 24 h; they remained unchanged throughout the following 48 h. These low levels, however, were reversible. Following 4 h incubation under 100% N2, sperm ATP levels rose upon exposure to and maintenance under 100% O2, increasing to 50% of initial values after a total of 72 h. ATP levels in sperm maintained with cyanide for 4 h decreased to less than 5% of initial values. The magnitude of the change in sperm ATP levels after 24 h in samples maintained under 100% O2 correlated positively with the initial sperm ATP levels. Sperm ATP levels, motility, and fertility were all correlated positively in a subset of samples examined. The initial percent of living sperm (sperm viability) was 97.5 ± 0.5% and was unaltered through 24 h under all O2 tensions. Sperm viability remained unchanged through 72 h under 21% O2 and decreased by 10 and 30% by 72 h under 100% O2 and 100% N2, respectively. Therefore, reductions in sperm ATP levels could not be attributed to cell death as viability decreased only modestly over these durations. Spermatocrit values were unaltered throughout the 72 h incubation for samples maintained under 100 and 21% O2, however, a 95% increase in spermatocrit occurred after 72 h in samples maintained under 100% N2. These data indicate that intracellular ATP in steelhead trout sperm can be modulated by ambient oxygen without significant loss of viability and that this ATP has a probable role in cell motility and fertility, and sperm packing and cell flexibility.