Sassoon D A, Gray G E, Kelley D B
Department of Biological Sciences, Columbia University, New York, New York 10027.
J Neurosci. 1987 Oct;7(10):3198-206. doi: 10.1523/JNEUROSCI.07-10-03198.1987.
We used histochemical techniques [assays for adenine triphosphatase (ATPase) and succinate dehydrogenase (SDHase) activity] to identify muscle fiber types in the larynx of Xenopus laevis. Male muscle is made up of one fiber type, medium-sized fibers (approximately 9 microns2) that stain lightly for acid-stable ATPase and intensely for SDHase activity. In contrast, the female has 3 fiber types: small fibers (approximately 6 microns2) that stain intensely for ATPase and SDHase, medium-sized fibers (approximately 13 microns2) with moderate staining for ATPase and dark staining for SDHase, and large fibers (approximately 15 microns2) with little SDHase or ATPase activity. Long-term castration (6 months) has no effect on histochemical staining of adult male fibers. Long-term testosterone treatment (5 months) increases the proportion of medium-sized, moderately staining fibers in adult females, and reduces the proportion of both the small, darkly staining fibers and the large, lightly staining fibers. At metamorphosis, both males and females have 3 fiber types whose ATPase activity is similar to that of the adult female. However, no SDHase activity is observed. Treatment of juveniles for 3 weeks with testosterone results in nearly complete masculinization of muscle fibers, as judged by increased cross-sectional area, homogeneous ATPase staining, and a marked increase in SDHase activity. Thus, juvenile muscle is considerably more responsive to testosterone than is adult female muscle. We propose that the uniform metabolic properties of male laryngeal muscle contribute to the production of the rapid (66 Hz) mate call vocalizations characteristic of this species. Further, our results suggest that androgens direct the masculinization of laryngeal muscle fibers during postmetamorphic development.
我们使用组织化学技术[三磷酸腺苷酶（ATPase）和琥珀酸脱氢酶（SDHase）活性测定法]来鉴定非洲爪蟾喉部的肌纤维类型。雄性肌肉由一种纤维类型组成，即中等大小的纤维（约9平方微米），其对酸稳定的ATPase染色浅，对SDHase活性染色深。相比之下，雌性有3种纤维类型：对ATPase和SDHase染色深的小纤维（约6平方微米）、对ATPase染色中等且对SDHase染色深的中等大小纤维（约13平方微米）以及SDHase或ATPase活性低的大纤维（约15平方微米）。长期去势（6个月）对成年雄性纤维的组织化学染色没有影响。长期睾酮治疗（5个月）会增加成年雌性中中等大小、染色中等的纤维比例，并降低小的、染色深的纤维和大的、染色浅的纤维的比例。在变态期，雄性和雌性都有3种纤维类型，其ATPase活性与成年雌性相似。然而，未观察到SDHase活性。用睾酮处理幼体3周后，根据横截面积增加、ATPase染色均匀以及SDHase活性显著增加判断，肌纤维几乎完全雄性化。因此，幼体肌肉对睾酮的反应比成年雌性肌肉要大得多。我们认为雄性喉部肌肉统一的代谢特性有助于产生该物种特有的快速（66赫兹）求偶叫声。此外，我们的结果表明雄激素在变态后发育过程中指导喉部肌纤维的雄性化。
