Acrossoma

Acrossomo é uma organela localizada na região frontal da cabeça do espermatozoide, contendo enzimas essenciais à sua penetração no ovócito e à fertilização.[1]

Estrutura

É uma estrutura semelhante a um capuz derivada do complexo de Golgi. A formação do acrossoma é completada durante a maturação dos testículos. Em mamíferos placentários a acrossoma contém enzimas digestivas(incluindo a hialuronidase e a acrosina).[2] Estas enzimas decompõem a membrana externa do ovócito, a chamada zona pelúcida, permitindo que o núcleo haplóide da célula do espermatozóide se junte ao núcleo haplóide do ovócito.[3]

Este derramamento do acrossoma, ou Reacção acrossómica, pode ser estimulado in vitro por substâncias que um espermatozoide pode encontrar naturalmente, tais como a progesterona ou fluido folicular, bem como o mais comumente utilizado cálcio ionóforo A23187. Isto pode ser feito para servir como um controle positivo quando se avalia a reacção do acrossoma de uma amostra de sêmen por citometria de fluxo[4] ou microscopia de fluorescência. Isto é geralmente feito após a coloração com fluoresceína de uma lectina, tais como FITC-PNA, FITC-PSA, com FITC-ConA, ou anticorpos fluorescentes, tais como CD46-FITC.[5]

Diagrama do espermatozoide humano

Infertilidade masculina

No caso de teratospermia (espermatozóides com cabeça redonda), o Complexo de Golgi não se transforma no acrossoma, causando infertilidade masculina.[6]

Referências

  1. ↑ Maria R. Borges-Osório; Wanyce M. Robinson. Genética Humana 3ed. ISBN 978-85-65852-90-6. p. 707.
  2. ↑ «acrosome definition - Dictionary - MSN Encarta». Consultado em 15 de agosto de 2007. Arquivado do original em 31 de outubro de 2009 
  3. ↑ Keith Moore. Embriologia Clínica. Elsevier Health Sciences Brazil; 27 June 2011. ISBN 978-85-352-4593-6. p. 119.
  4. ↑ Miyazaki R, Fukuda M, Takeuchi H, Itoh S, Takada M (1990). «Flow cytometry to evaluate acrosome-reacted sperm». Arch. Androl. 25 (3): 243–51. PMID 2285347 
  5. ↑ Carver-Ward JA, Moran-Verbeek IM, Hollanders JM (fevereiro de 1997). «Comparative flow cytometric analysis of the human sperm acrosome reaction using CD46 antibody and lectins». J. Assist. Reprod. Genet. 14 (2): 111–9. PMID 9048242 
  6. ↑ Hermann Behre; Eberhard Nieschlag (2000). Andrology : Male Reproductive Health and Dysfunction. Berlin: Springer. p. 155. ISBN 3-540-67224-9 

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