Embryo development is impaired by sperm mitochondrial-derived ROS

BACKGROUND: Basal energetic metabolism in sperm, particularly oxidative phosphorylation, is known to condition not only their oocyte fertilising ability, but also the subsequent embryo development. While the molecular pathways underlying these events still need to be elucidated, reactive oxygen species (ROS) could have a relevant role. We, therefore, aimed to describe the mechanisms through which mitochondrial activity can influence the first stages of embryo development. RESULTS: We first show that embryo development is tightly influenced by both intracellular ROS and mitochondrial activity. In addition, we depict that the inhibition of mitochondrial activity dramatically decreases intracellular ROS levels. Finally, we also demonstrate that the inhibition of mitochondrial respiration positively influences sperm DNA integrity, most likely because of the depletion of intracellular ROS formation. CONCLUSION: Collectively, the data presented in this work reveals that impairment of early embryo development may result from the accumulation of sperm DNA damage caused by mitochondrial-derived ROS.

Determination of optimal glucose concentration for microcalorimetric metabolic evaluation of equine spermatozoa

The heat conduction microcalorimeter can be used to evaluate the metabolic rates of the sperm cell. Two ejaculates of four stallions were cooled to +5ºC and checked for sperm motility (bright field microscopy), viability (eosin 3 percent), functional membrane integrity (hyposmotic swelling test), and heat production (microcalorimetry). Glucose and sperm cell concentrations were determined in order to measure the heat outputs resulting from sperm metabolism. Sperm viability, membrane integrity and sperm motility did not differ among the different glucose concentrations tested. Nevertheless, the highest heat output detected by the microcalorimeter was obtained with 6 mM glucose and 10(8) spermatozoa/mL. Since conduction microcalorimetry offered additional information on equine sperm metabolism, it could be used as a method to study equine semen preservation.

O microcalorímetro de condução pode ser usado para avaliar as taxas metabólicas do espermatozóide eqüino. Dois ejaculados de quatro garanhões foram avaliados quanto à motilidade progressiva pela microscopia, viabilidade espermática (eosina 3 por cento), integridade funcional da membrana (teste hiposmótico) e produção de calor (microcalorimetria). Concentrações ótimas de glicose e de células espermáticas foram determinadas, para mensurar o calor liberado resultante do metabolismo espermático em relação à capacidade de detecção do calor pelo microcalorímetro. Não foi observada diferença da motilidade, viabilidade e integridade funcional de membrana espermática quando adicionada glicose nas três concentrações estudadas. No entanto a avaliação por microcalorimetria ressaltou um maior fluxo de calor a uma concentração de 6 mM de glicose e uma concentração espermática de 10(8) espermatozóides/mL. Portanto, a técnica de microcalorimetria oferece informações adicionais sobre o metabolismo tornando-se uma ferramenta importante no estudo do processo de preservação do sêmen eqüino.