胰腺β细胞过度表达人类ras原癌蛋白质(oncoprotein)的转基因小鼠,90%多5～8月龄雄性鼠发生β细胞变性及糖尿病。相反,尽管雌性小鼠表达与雄性小鼠相当水平的原癌蛋白质,但大多数雌鼠β细胞可抵抗ras基因的作用,血糖也维持正常,直到超过2岁。这种性别的二型现象的产生可能有激素基础或者可能是 Transgenic mice overexpressing human ras oncoprotein by pancreatic β cells develop β-cell degeneration and diabetes in more than 90% of males aged 5 to 8 months. In contrast, although female mice express comparable levels of oncogenic proteins in male mice, most female rat β cells resist the effect of the ras gene and blood glucose levels remain normal until age 2 years or older. This type of second sex phenomenon may have a hormonal basis or may be