RESUMEN
This study extends to the protein level our previous observations, which had established the stage and cellular specificity of expression of hsp86 and hsp84 in the murine testis in the absence of exogenous stress. Immunoblot analysis was used to demonstrate that HSP86 protein was present throughout testicular development and that its levels increased with the appearance of differentiating germ cells. HSP86 was most abundant in the germ cell population and was present at significantly lower levels in the somatic cells. By contrast, the HSP84 protein was detected in the somatic cells of the testis rather than in germ cells. The steady-state levels of HSP86 and HSP84 paralleled the pattern of the expression of their respective mRNAs, suggesting that regulation at the level of translation was not a major mechanism controlling hsp90 gene expression in testicular cells. Immunoprecipitation analysis revealed that a 70-kDa protein coprecipitated with the HSP86/HSP84 proteins in testicular homogenates. This protein was identified as an HSP70 family member by immunoblot analysis, suggesting that HSP70 and HSP90 family members interact in testicular cells.
Asunto(s)
Regulación de la Expresión Génica , Proteínas de Choque Térmico/análisis , Espermatocitos/química , Espermatogénesis , Testículo/química , Animales , Diferenciación Celular/genética , Electroforesis en Gel de Poliacrilamida , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/fisiología , Immunoblotting , Masculino , Ratones , Peso Molecular , Especificidad de Órganos , Pruebas de Precipitina , Biosíntesis de Proteínas , Testículo/citología , Testículo/crecimiento & desarrolloRESUMEN
Testes from flight rats on COSMOS 2044 and simulated-launch, vivarium, or caudal-elevation control rats (5/group) were analyzed by subjective and quantitative methods. On the basis of observations of fixed tissue, it was evident that some rats had testicular abnormalities unassociated with treatment and probably existing when they were assigned randomly to the four treatment groups. Considering rats without preexisting abnormalities, diameter of seminiferous tubules and numbers of germ cells per tubule cross section were lower (P less than 0.05) in flight than in simulated-launch or vivarium rats. However, ratios of germ cells to each other or to Sertoli cells and number of homogenization-resistant spermatids did not differ from values for simulated-launch or vivarium controls. Expression of testis-specific gene products was not greatly altered by flight. Furthermore, there was no evidence for production of stress-inducible transcripts of the hsp70 or hsp90 genes. Concentration of receptors for rat luteinizing hormone in testicular tissue and surface density of smooth endoplasmic reticulum in Leydig cells were similar in flight and simulated-launch rats. However, concentrations of testosterone in testicular tissue or peripheral blood plasma were reduced (P less than 0.05) in flight rats to less than 20% of values for simulated-launch or vivarium controls. Thus spermatogenesis was essentially normal in flight rats, but production of testosterone was severely depressed. Exposure to microgravity for greater than 2 wk might result in additional changes. Sequelae of reduced androgen production associated with microgravity on turnover of muscle and bone should be considered.
Asunto(s)
Vuelo Espacial , Testículo/fisiología , Ingravidez/efectos adversos , Animales , Gonadotropina Coriónica , Regulación de la Expresión Génica/fisiología , Marcadores Genéticos , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Células Intersticiales del Testículo/fisiología , Masculino , Ratones , Ratones Endogámicos , Tamaño de los Órganos/fisiología , Ratas , Ratas Endogámicas , Espermatogénesis/fisiología , Testículo/anatomía & histologíaRESUMEN
The expression of members of the heat shock protein 90 (hsp90) gene family during testicular and embryonic development was investigated. Two different hsp90 transcripts were detected in RNA from mouse testis, approximately 3.2 kb and 2.9 kb in size, and were shown to exhibit cellular and developmental stage specificity of expression. The larger, more abundant transcript was expressed at high levels in the germinal compartment of the testis, particularly in germ cells in meiotic prophase. The smaller hsp90 transcript was expressed predominantly in the somatic compartment of the testis. Expression of the two hsp90 transcripts was observed in testes of other species, suggesting an important role for hsp90 in mammalian testicular function. In addition, expression of both hsp90 transcripts was detected in the embryonic and extra-embryonic compartments of mid-gestation embryos.