. Study of the evolution of boar spermatozoa populations according to their response to short HOST and their acrosomal status during preservation at 15ºC.
B.Pérez-Llano, R.Sánchez-Sánchez, P.Yenes-García and P.García-Casado.6th International Conference on Pig Reproduction Missouri 3-6 June 2001. Abst.50. The tests used in the routine evaluation of boar ejaculate give us biased data about semen quality. Motility or vital stain only indicate viability, the study of the acrosomes only shows if this part of the spermatozoa is damaged or not, HOS test seems to demonstrate damage only in the plasma membrane of the sperm tail. In preliminary works we have observed that short HOST (sHOST), a modification of the original HOST, was the test that presented a higher correlation with fertility (r = 0.4. p<0.01), in selected ejaculates with a low percentage of abnormal sperm. However, the correlation between sHOST and the percentage of normal acrosomes in fresh ejaculates was low. The aim of this work is to study the relationship between the sperm population with different sHOST results and different percentage of normal acrosomes. In other words, if there is some relationship between the damage of the plasma membrane of the head and that of the tail of the boar spermatozoa. A total of fifteen dosis of fifteen different boars were used. All of them presented a percentage of coiled tails and/or proximal droplets lower than 20%. They were diluted after collection in farm (1:10 semen:extender), sent to our lab and preserved at 15ºC during 7 days. Every day a sample of every ejaculate was taken and warmed up to 37ºC. Then, a sample of 0.35 ml was submitted to 1 ml of an hyposmotic solution (75 mOsm/kg) during 5 minutes in a water bath at 37ºC. Then, a sample of 0.35 ml was taken and fixed in 0.5 ml of a 2% glutaraldehyde solution. In a phase contrast microscope (X1000) we classified in every sample 100 cells into one of these four categories or populations: sHOST positive with normal acrosomes (HPNA), sHOST positive with damaged acrosomes (HPDA), sHOST negative with normal acrosomes (HNNA) and sHOST negative with damaged acrosomes (HNDA). An ANOVA was used to study differences between populations along the preservation period. In table 1 mean ± SE of the four populations of spermatozoa along the preservation period are shown. The populations were distributed as follows: HNNA 25.5%, HPNA 28.9%, HNDA 29.3% and HPDA 16.2%. Of the total of sHOST positive cells (HPNA+HPDA: 45.1%), a 64% presented normal acrosomes. This is the cell population with the plasma membrane most resistant to damage due to preservation. This population decreased significantly (p<0.05) along the preservation period. Of the total of sHOST negative cells (HNNA+HNDA: 54.8%), a 53% presented damaged acrosomes. This is the cell population with the less resistant plasma membrane. This population increases significantly (p<0.05) along the preservation period. On the other hand, the sHOST positive population, presented a percentage of damaged acrosomes significantly lower (p<0.01) than the sHOST negative population. This indicates a higher resistance of the plasma membrane of the whole spermatozoa in sHOST positive cells. This difference was maintained along all the preservation period, with a significant increase (p<0.05) of the damaged acrosomes of the sHOST negative population compared to the damaged acrosomes of the sHOST positive cells that did not increase. This indicates again a better quality of the plasma membrane of the sHOST positive cells. These results show that the evaluation of sHOST in boar ejaculates informs us not only about the status of the plasma membrane of the tail but also about the status of the plasma membrane of the sperm head.
