(C) RT-PCR analysis of SPEM1 in 17 human organs. ACTIN was used a loading control. (D)Western blot analysis of SPEM1 protein expression in 10 mouse organs. ACTIN was used as a loading control.我在翻译文献 不知道这里面的loading control是什么意思啊 谁能帮助一下 万分感谢啊