Compactação da cromatina e morfometria de espermatozóides bovinos selecionados e capacitados

Abstract

Aiming to improve the efficiency in obtaining viable embryos in in vitro fertilization procedures, sperm selection and concentration methods are used. However little is known about the action of these methods on the chromatin condensation and sperm head morphometry. Likewise the effect of sperm in vitro capacitation on these characteristics is controversial. This study evaluated the effect of sperm selection by Percoll gradient, "swim-up procedure and sperm capacitation in vitro by heparin on chromatin condensation and sperm head morphometry of cattle. Eighteen semen samples were subjected to both methods of selection and subsequent capacitation tests. Smears were made at every stage and stained by the metachromasia method induced by toluidine blue (AT). The scanned images were processed in software developed in an SCILAB environment. It was observed that after selection by gradient of Percoll and "swim up" the sperm tend to have looser and more heterogeneous chromatin. The "swim up" method selected heads more symmetrical, smoller and with less size variation when compared to the same semen sample prior to selection. After heparin-induced capacitation the spermatozoa presented looser crhomatin and slight change of the head.