Kishimoto Ayuko, Ishiguro-Oonuma Toshina, Takahashi Ritei, Maekawa Mamiko, Toshimori Kiyotaka, Watanabe Masahiko, Iwanaga Toshihiko
Department of Anatomy, Graduate School of Medicine, Hokkaido University.
Biomed Res. 2015;36(4):225-34. doi: 10.2220/biomedres.36.225.
Lactate represents a preferential energy substrate of germ cells rather than glucose. Testicular Sertoli cells are believed to produce lactate and pyruvate and to supply these to germ cells, particularly spermatocytes and spermatids. Monocarboxylate transporter (MCT), responsible for the transport of lactate and other monocarboxylates via the cell membrane, is abundant in the testes and sperm (MCT1, MCT2, and MCT4). For the uptake of glucose, germ cells within the seminiferous tubules and sperm have been known to intensely express GLUT3. The present study investigated expression profiles of MCTs and GLUTs and revealed their cellular and subcellular localization in the mouse and rat testis. An in situ hybridization analysis showed significant expressions of MCT1, MCT2, and GLUT3 mRNA in the testis. Immunohistochemically, spermatogonia, spermatocytes, and spermatids expressed MCT1 on their cell surfaces in a stage-dependent manner: in some seminiferous tubules, an intense expression of MCT1 was unique to the spermatogonia. MCT2 was restricted to the tails of elongated spermatids and sperm. An intense immunoreactivity for GLUT3 was shared by spermatocytes, spermatids, and sperm. Sertoli cells were devoid of any immunoreactivities for MCT1, MCT2, and GLUT3. The predominant energy source of germ cells may be lactate and other monocarboxylates--especially for spermatogonia, but glucose and other hexoses may be responsible for an energy supply to spermatocytes and spermatids.
乳酸是生殖细胞而非葡萄糖的优先能量底物。睾丸支持细胞被认为可产生乳酸和丙酮酸，并将其供应给生殖细胞，尤其是精母细胞和精子细胞。负责通过细胞膜转运乳酸和其他单羧酸的单羧酸转运体（MCT）在睾丸和精子中大量存在（MCT1、MCT2和MCT4）。已知生精小管内的生殖细胞和精子强烈表达葡萄糖转运蛋白3（GLUT3）以摄取葡萄糖。本研究调查了MCT和GLUT的表达谱，并揭示了它们在小鼠和大鼠睾丸中的细胞及亚细胞定位。原位杂交分析显示睾丸中MCT1、MCT2和GLUT3 mRNA有显著表达。免疫组织化学结果显示，精原细胞、精母细胞和精子细胞在其细胞表面以阶段依赖性方式表达MCT1：在一些生精小管中，MCT1的强烈表达是精原细胞所特有的。MCT2局限于伸长的精子细胞和精子的尾部。精母细胞、精子细胞和精子均对GLUT3有强烈免疫反应。支持细胞对MCT1、MCT2和GLUT3均无免疫反应。生殖细胞的主要能量来源可能是乳酸和其他单羧酸——尤其是精原细胞，但葡萄糖和其他己糖可能为精母细胞和精子细胞提供能量。
