An In Vitro Evaluation of Biochemical Processes Involved in Lead‐Induced Changes on Ram Spermatozoa

Abstract

Lead (Pb(2+) ) is a toxic heavy metal which interferes with several physiological processes regulated by Ca(2+) , including those characterized by changes of the membrane stability and the motility of spermatozoa necessary for the fertilization of the oocyte. In this study, ejaculated sperm from six rams (Ovis aries) have been incubated in vitro with or without 50 ng Pb(2+) /ml during 30 min and in the presence or absence of three different potential modulators of the effects of Pb(2+) on changes in the sperm membrane before fertilization: charybdotoxin, quinacrine and staurosporine. Sperm samples incubated with Pb(2+) have shown significant reductions in acrosome integrity and sperm viability and an increase in progressive movement. None of the studied potential modulators had a protective effect against Pb(2+) action. On the contrary, Pb(2+) -incubated sperm in the presence of staurosporine had lower acrosome integrity, and lower sperm viability was observed when spermatozoa were incubated with Pb(2+) + charybdotoxin. Quinacrine was the only tested substance capable of increasing the concentration of Pb(2+) in spermatozoa; thus, the enhancement of Pb(2+) effects produced by staurosporine and charybdotoxin was not produced by an increased uptake of Pb(2+) by spermatozoa. However, the increase of intracellular Pb(2+) in those spermatozoa incubated with quinacrine did not result in an adverse effect on sperm motility or viability although the acrosome integrity was negatively affected.

Effects of Lead Exposure on Sperm Quality and Reproductive Success in an Avian Model

“…This increase in sperm vigor has been also observed in sperm of rams incubated in vitro with Pb. 70 Pb 2+ interacts with a number of Ca 2+ dependent effectors such a calmodulin (a Ca 2+ receptor protein) and Ca 2+ -dependent K + channels in the plasma membrane, but also with enzymes such as protein kinase C and phospholipases; these can activate cytoplasm alkalinization, membrane hyperpolarisation, sperm motility, membrane permeability, and acrosome reaction. 70−73 Therefore, the observed increased sperm vigor and the reduced acrosome integrity can result from the interaction of Pb 2+ with physiological mechanisms mediated by Ca 2+ to produce the capacitation process of spermatozoa.…”