Lipid analysis of human spermatozoa and seminal plasma by MALDI-TOF mass spectrometry and NMR spectroscopy - effects of freezing and thawing

In the present study, the applicability of proton NMR spectroscopy and matr ix-assisted laser desorption and ionization time-of-flight mass spectrometr y (MALDI-TOF MS) to the analysis of the lipid composition of human spermato zoa and seminal fluids as well as changes after cryopreservation of human s permatozoa was investigated. Whereas NMR spectra primarily indicated a high content of double bonds within the spermatozoa but no marked differences u pon cryopreservation, MS detected intense peaks which could be assigned to phosphatidylcholines containing one docosahexaenoic and one palmitic or ste aric acid residue (m/z = 806 and 834). In contrast, the seminal plasma cont ained more saturated fatty acids and especially more sphingomyelin (SM). A freezing/thawing cycle markedly influences the lipid composition of spermat ozoa. There was a diminution of phosphatidylcholines (16:0, 22:6 and 18:0, 22:6) and SM (16.0) and the appearance of lysophosphatidylcholines (16:0 an d 18:0) and ceramide (16:0). These data demonstrate the release or activati on of both phospholipase A(2) and sphingomyelinase in human spermatozoa due to the freezing/thawing cycle. These results were finally confirmed by exp eriments on the action of phospholipases on lipids containing docosahexaeno ic acid. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.