MONTHS 130 m

FIG. 5. Effect of ageing on iNOS levels in the rat hypothalamus. Top panel, autoradiography of the 130 kDa bands on a typical Western blot of the postmitochondrial supernatants (80 mg protein/lane) with an antibody against mouse iNOS and visualization with a luminol reaction. Middle panel, Mean intensity of the respective bands determined by densitometry compared with younger adults. The expression of iNOS assessed by Western blot assay was present in 3 month old animals but increased by 2.5-fold in the relatively normal testes and fourfold in the regressed testes of the old rats. No significant changes were noted in nNOS levels between the testes obtained from young or old animals. Immunohistochemistry showed that iNOS expression was most striking in Leydig cells with little or no immunoreactivity in the Sertoli and germ cells of young rats. In contrast, there was a marked increase in iNOS immunoreactivity in the Sertoli cells and some staining in the germ cells of old rats. Neuronal NOS was detectable in Leydig and Sertoli cells in both young and old animals but unlike iNOS, no age-related differences were apparent. Our results showed that ageing in the BN rats, in a similar fashion to changes in the hypothalamus and other brain regions, was associated with iNOS induction and high iNOS synthesis in the testis. We also speculate that the increased iNOS through the formation of cytotoxic products may be an important mediator of age-related activation of germ cell apoptosis.

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