| The effects of aging on testicular function in male ratsIn contrast to the female, the effects of ageing on testicular function in the male have been debated for decades. The main causes are that the decrease of testicular function with aging is of a progressive course without a cut-point, and the serum level of T in the aging male has markedly individual variation. However, in recent years some cross-sectional and longitudinal studies have convincingly demonstrated that serum T levels decrease with aging, even when taking into account the influential factors, such as the hour of sampling, suffering from chronic illness, medications, and assays. A longitudinal study of 890 men at the age of 22- 91 year old showed that the incidence of hypogonadism was about 20% in men over 60, 30% over 70 and 50% over 80 years by TT judgement, and the percentages were even greater by judgement of free T index. By Massachusetts Male Aging Study also presented that at least 4% of asymptomatic men, aged 40-70 years, had severe androgen deficiency as indicated by serum T concentrations less than 150ng/dL in association with elevated LH concentrations. The nomination of partial androgen deficiency of the aging male (PADAM) by Austria Urology Association has been widely accepted. The men with PADAM will experience poor general well-being, depression, impaired cognitive function, decrease of muscle mass, energy and hemoglobin and increaseof visceral fat, insulin resistance, osteoporosis and erectile dysfunction. It has been thought that the decline of serum T with aging basically is due to the testicular impairment. For the limited source of human testis specimen, testes of rats are the good replacements in laboratory use. The purpose of this study was to investigate the age-related changes of testicular steriodogenic function and testicular morphology in SD rat. The study contained two parts.Part 1. The effects of ageing on the testicular steroidogenic function in rats.Aim: To investigate the effects of aging on the hormone and steroidogenic enzymes in aging SD rats. Method: The young (aged 3 mo) and the aging (aged 24 mo) SD rats were used in this study. The rats were classified as young control group, young hCG-treated group, aging control group and aging hCG-treated group based on age and the present or absent of hCG treatment. Serum level of T, E2 and the ratio of E2/T were observed, and the mRNA expression levels of StAR, P450scc, IVp-HSDHI and P450arom were determined by RT-PCR. Results: Comparing to young rats, the serum T concentration in aging rats was significantly reduced up to 82%. The serum E2 concentrations between the young and aging rats were similar, but significant increase of E2/T ratio was seen in the aging rats, no matter at baseline or after hCG treatment. After hCG treatment, the peak value of serum T concentrationin aging group was significantly lower than that in young group. No significant age-related change was found in StAR mRNA. The testicular levels of P450scc and 17p-HSDlII mRNA in aging rats were significantly decreased by 46% and 61% respectively than those in young rats. The StAR mRNA level of aging hCG group increased significantly under hCG stimulation and was not different from young rats; The level of P450scc mRNA in young hCG group was lower than that in young control group, and there was no change between aging hCG group and aging control group; The levels of 17P-HSDIII mRNA in both of aging rats and young rats were significantly increased in the presence of hCG Anyway, the increment of 17|3-HSDIII mRNA in aging hCG group was much lower (up to 64%) than that in young hCG group. There wasn't significant difference in P450arom mRNA between aged and young SD rats. Conclusions: Serum T concentration was reduced and the ratio of E2/T was elevated in aging SD rats. The response of testes to hCG in aging SD rats was low in contrast to the young SD rats. This result suggested that there are the age-related testicular defects. The reduced response of testes to hCG in aging SD rats demonstrate...
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