On osmolality and sperm function during processing for assisted reproduction

Deep basic knowledge about sperm physiology is relevant and important to optimize the outcome of procedures used during Assisted Reproductive Technologies (ART) to select spermatozoa for fertilization. More specifically, this study examined osmolality changes and consequences for sperm motility and sperm selection in the laboratory. What kind of environmental changes occur and what challenges must the spermatozoa endure after leaving the body? How do these challenges affect the spermatozoa’s functions, fertilizing potential and the make-up of the genetic material they will deliver to the oocyte? In study I, the objective was to measure the changes in osmolality that occur after collecting the ejaculate in the laboratory. After ejaculation, the sample is mixed in order to make it homogenous. This will cause the different fractions that make up the semen sample to mix. A total of 348 individual ejaculates, 5 split ejaculates and 6 ejaculate pools were studied, and it appeared that there was an individual pattern of change in osmolality over time. At 3 hours after the ejaculation, the change in osmolality ranged from 2 mOsm/kg to 164 mOsm/kg. Furthermore, it was evident that the change in osmolality was temperature dependent. Samples stored at 37°C increased significantly more in osmolality than samples stored at 18-22°C, than samples stored at 4-7°C and than samples stored at -20°C. Denaturising temperature (100°C) blocked any further increment in osmolality. One probable cause of the increase in osmolality is that the enzymes, which are abundant in the prostatic fluid, are degrading macro-molecules, such as the proteins that are abundant in the seminal vesicular fluid. When these two secretions are mixed, the enzymatic degradation can start (Mann and Lutwak–Mann, 1981). In study II, the markers for the different fractions of the ejaculate were measured in order to relate to the change in osmolality. As well as containing high levels of proteins, the seminal vesicular fluid also contains relatively high levels of ...