Key Event Title
|Level of Biological Organization|
Key Event Components
Key Event Overview
AOPs Including This Key Event
|AOP Name||Role of event in AOP|
|Histone deacetylase inhibition leading to testicular atrophy||KeyEvent|
|Rattus norvegicus||Rattus norvegicus||Moderate||NCBI|
Key Event Description
The apoptosis of the cells lead to spermatocyte depletion. Spermatocytes are differentiated from spermatogonial stem cells via random proliferation, differentiation and synchronized mitoses with several stages [Rooij, 2001].
How It Is Measured or Detected
The sperm-containing fluid was squeezed out of the cauda, and suspended in medium containing HEPEs buffer and bovine serum albumin, and incubated at 37C for 20 min. The number of spermatozoa was determined by hematocytometer [Zindy, 2001].
Testicular sperm counts and daily sperm production were determined by counting the total number of spermatids per testis, and divided by the testicular weight to give the results in spermatids per gram of testis [Oishi, 2001].
For the detection of apoptosis, the testes were fixed in neutral buffered formalin, and embedded in paraffin. Germ cell death was visualized in testis sections by Terminal dUTP Nick End-Labeling (TUNEL) staining memthod [Wade, 2008]. The incidence of TUNEL-positive cells was expressed as the number of positive cells per tubule examined for one entire testis section per animal [Wade, 2008].
For the testis cell analysis, fresh testes were dispersed using a two-stage enzymatic digestion and incubated in BSA containing collagenase and DNase I [Wade, 2006]. The seminiferous tubules were further digested and cells were fixed in ice-cold 70% ethanol [Wade, 2006]. Relative proportions of spermatogenic cell populations were assessed in fixed cells using a flow cytometeric method [Wade, 2006]. The principle of the test is that spermatogenic cells, as they differentiate from normal diploid spermatogonial stem cells through to mature spermatozoa with a highly condensed haploid complement of DNA, progress through various intermediate stages with differing nuclear DNA content and cellular content of mitochondria. Relative proportions of cells in each population were calculated with WinList software [Wade, 2006].
Domain of Applicability
There are evidences of spermatocyte depletion.
・It has been reported that mice lacking cyclin D-dependent kinase inhibitor proteins produced few mature sperm, and the residual spermatozoa had reduced motility and decreased viability (Mus musculus) [Zindy, 2001].
・The sperm counts in the cauda epidydimis of rats exposed to butylparaben were significantly decreased (Rattus norvegicus) [Oishi, 2001].
・MAA treatment induced spermatocyte death in Sprague-Dawley rats (Rattus norvegicus) [Wade, 2008].
Rooij DG. (2001) Proliferation and differentiation of spermatogonial stem cells. Reproduction 121:347-354
Zindy F et al. (2001) Control of spermatogenesis in mice by the cyclin D-dependent kinase inhibitors p18Ink4c and p19Ink4d. Mol Cell Biol 21:3244-3255
Oishi S. (2001) Effects of butylparaben on the male reproductive system in rats. Toxicol Indust Health 17:31-39
Wade MG et al. (2008) Methoxyacetic acid-induced spermatocyte death is associated with histone hyperacetylation in rats. Biol Reprod 78:822-831
Wade MG et al. (2006) Testicular toxicity of candidate fuel additive 1,6-dimethoxyhexane: comparison with several similar aliphatic ethers. Toxicol Sci 89:304-313