Efeito do campo eletromagnético de baixa frequência e do choque térmico nas células gonadais de ratos

Abstract

In recent decades, humans have been exposed to various exogenous physical agents, such as high temperatures emitted by industrial devices and electromagnetic fields emitted by the electricity distribution networks and electronic devices. Researches demonstrated that these agents can cause reproductive disorders. The chapter 1 of this study aimed to investigate the possible effects of low frequency EMF exposure of 60 Hz and 1 mT from day 13 of gestation up to puberty at 21 postnatal days. The results showed that exposure to EMF reduced parameters related to the lumen, epithelium and seminiferous tubules. It was also observed an increase in the volume of blood vessels and connective tissue cells in animals exposed to EMF. The plasma testosterone did not change due to EMF exposure. The exposure to EMF of 60 Hz and 1 mT from gestation to puberty can induce a delay in testicular development. In chapter 2, the aim was to evaluate the effects of exposure to low frequency EMF (60 Hz and 1 mT) from the 13th day of gestation up to 90 postnatal days (adult). The plasma testosterone concentration was not changed by EMF exposure. However, the histopathological and histomorphometrical analysis showed testicular degeneration in a subset of animals exposed to EMF. The degenerative process severity varied among affected animals, indicating an individual sensitivity to EMF. The electron microscopy analysis also showed testicular degeneration, the main change was high electrodense mitochondria with loss of normal organization and cristae. The exposure to EMF of 60 Hz and 1 mT seems to alter spermatogenesis and reduce the fertility. Chapter 3 aimed to analyze the effects of heat shock (43 °C / 15 min.) and Hsp90 inhibition on CaV3 T-type calcium channels and calciumactivated potassium channels (BKCa) in Leydig cells. The results showed that exposure to heat shock induced a reduction in BKCa channels steady-state current (49.8%), maximum conductance (68.9%) and activation time constant (31.9%). Heat shock slowed the BKCa channels activation and reduced its voltage dependence. Hsp90 inhibition did not change BKCa channels. The CaV3 channels current was not affected by heat shock or Hsp90 inhibition. The heat shock can inhibit BKCa channels, the Hsp90 does not seem to be involved in this process.