ATP Content and Adenine Nucleotide Catabolism in African Catfish Spermatozoa Stored in Various Energetic Substrates

Influence of various energetic substrates on ATP content and adenine nucleotide catabolism in African catfish, Clarias gariepinus spermatozoa was investigated. Present data indicate that sperm storage at 4 °C in the presence of different energetic substrates leads to time dependent ATP depletion. Among the substrates studied (i.e. glycine, glucose, or lactate plus pyruvate), the lactate plus pyruvate seems to be the most favourable substrate to maintain ATP concentration. ATP depletion is associated with increase of the AMP content, while ADP concentration is changing only slightly. Moreover, significant increase in hypoxanthine content both in the sperm and a storage medium was found. Adenine nucleotide energy charge (AEC) decreased significantly during the first 24 h when sperm was stored in the presence of glycine. During the same period, only slight decrease in AEC was observed in spermatozoa stored in the presence of glucose and no significant changes were found in the presence of lactate plus pyruvate. A further decrease in AEC was observed until 120 h of storage in the medium containing glycine, lactate plus pyruvate or glucose. However, the changes were relatively small when spermatozoa were stored in the presence of lactate plus pyruvate. Important finding is that in contrast to the results reported recently, AEC value in fresh milt (at 0 time of storage) was in the normal range. The present study shows that African catfish spermatozoa are able to maintain physiological level of ATP and AEC when they are stored in the presence of favourable energetic substrates. In conclusion, the results of this investigation suggest that successful short-term storage of African catfish milt depends on energetic substrates supply.