Adenine nucleotides and selected chemical Parameters as potential markers for fertility assessment

Abstract

Diagnostic andrology with its descriptive approach to the diagnosis of defective sperm for the last 40 years has focused mainly on the macro- and microscopic appearance of the ejaculate. More emphasis has recently been placed on the quantification of biochemical components in semen and sperm. In this regard, substances can be measured more accurately and in some cases as multi-components in the same run. The value of bioenergetics of sperm as a marker for fertility assessment is a controversial topic in the literature. What complicates this issue is the relatively new information on how adenosine triphosphate (ATP), as the major high energy molecule, can be synthesized from other sources which c/as, until recently, unknown. This study attempts to investigate the role of adenine nucleotides as potential markers in semen for fertility assessment using the Tygerberg strict criteria. In this study a reverse phase liquid chromatography (RPLC) technique was developed which measures all the nucleotides in a single run. Because the cycle of energy yielding and energy consuming processes operate simultaneously, it is difficult to assess the energy status of spermatozoa by only measuring the ATP concentrations as suggested in the literature. In this study all the adenine nucleotides and their relative ratios were measured. The results did not show significant differences using the Tygerberg strict criteria of morphology evaluation. This is in line with some workers who indicate that there is no value in measuring ATP levels and correlating this with fertilization. This study furthermore indicates that the breakdown products of ATP and the different adenine nucleotide ratios do not correlate positively with morphology and fertilization in the IVF and GIFT procedures using the Tygerberg strict criteria of morphology. As an application of the technique preliminary experiments indicated that the duration of incubating semen or spermatozoa is important when measuring nucleotides. An unknown product, that relates to motility, is formed during the incubation period of 18 hours (absent after 40 minutes). It was also shown in this preliminary study that the ATP/ADP ratio is the most sensitive biochemical parameter for changes in motility and that the older concept of the adenylate energy charge (AEC) is not a good indicator of the energy status of spermatozoa. The experiments with the energy related enzymes Lactate dehydrogenase and Creatine kinase versus the morphological groups, have been proved not to be predictive. The sperm membrane enzyme y-glutamyl transferase which also correlates negatively with the Tygerberg morphological groups could be more informative if the number of the P Pattern group (<4o/o) were increased. This membrane enzyme could be of more value than previously realized, since it may relate to the lipid peroxidation of sperm which are extremely susceptible to oxidative stress.