Abstract. Gonadal functions, with special reference to blood levels of sex-related markers such as 17b-estradiol (E2), free testosterone (free Te) and lutenizing hormone (LH), were examined in male OLETF (Otsuka Long Evans Tokushima Fatty) diabetic rats, a model of human type 2 diabetes mellitus. Male rats of the OLETF strain and male rats of the LETO strain, which act as a control of OLETF, both supplied by Otsuka Pharmaceutical Co., Ltd. (Tokushima, Japan), were periodically examined for blood levels of E2, free Te and LH at the age of 4, 5, 32, 40 and 64 weeks. The weight of the testis, the number of sperm contained within and histological findings of the testis were comparatively studied in both strains. Glucose and insulin (IRI) at fasting were examined to evaluate the homeostasis model assessment (HOMA) index. In order to investigate any sex hormone imbalance, sex hormone-binding globulin (SHBG) was measured by a dextrancharcoal assay. All of the OLETF rats became diabetic at the age of 32 weeks. There were no significant differences between OLETF and LETO rats regarding free Te, E2, LH or SHBG during the observation period from 4 to 64 weeks. Testis weight was significantly decreased in OLETF rats at 32 and 64 weeks and sperm counts at 64 weeks of age were also significantly decreased. Histologically, there was seminiferous tubule atrophy in the OLETF rats at 64 weeks of age. A significant negative correlation between testis weight and fasting blood glucose, as well as HOMA index, was observed in OLETF rats. In male diabetic OLETF rats, with a variety of hypogonadisms such as atrophy of the testis and low sperm count, the serum levels of E2, free Te, LH and SHBG were normally preserved. [5,6]. From about 20 weeks of age, OLETF rats begin to develop diabetes accompanied by obesity, and almost all of the rats develop diabetes by the age of 30 weeks. This study was intended to make clear, whether sexual dysfunctions, if any, occur in diabetic OLETF rats by examining serum levels of sex-related hormones and sex hormone-binding globulin (SHBG), as well as testis findings. SHBG is a factor affecting sex hormone activities by binding both testosterone and 17b-estradiol (E2), with a higher affinity for the former [7,8].
Materials and Methods
AnimalsBoth OLETF rats and their controls, named LETO (Long-Evans Tokushima Otsuka) rats, which are nondiabetic, were supplied by Otsuka Pharmaceutical Co., Ltd. (Tokushima, Japan). OLETF rats comprising 4, 5, 32, 40 and 64 weeks of age and control LETO rats corresponding to each OLETF age were studied. After
