Griswold M D
Program in Biochemistry and Biophysics, Washington State University, Pullman 99163.
Int Rev Cytol. 1988;110:133-56. doi: 10.1016/s0074-7696(08)61849-5.
As was stated in the introduction, many of the functions of the Sertoli cells are apparently carried out by the protein secretions of these cells. The use of Sertoli cell cultures and appropriate biochemical and immunological techniques has allowed the characterization of some of these secretion products. It is likely that many of the functions of the Sertoli cells are necessary because of the presence of the blood-testis barrier. Many growth and nutritive factors which are necessary for cell viability are available to most cells via the serum. The germinal cells within the adluminal compartment do not have access to serum factors and one of the functions of the Sertoli cells is to synthesize serum-like components and secrete them into the adluminal compartment. The historical description of Sertoli cells as "nurse cells" thus appears to have been accurate. The nurse-cell function is most clearly demonstrated by the proposed mechanism by which germinal cells obtain ferric ions. The Sertoli cells have developed a system to move serum-derived iron through their own cytoplasm and to secrete it bound to newly synthesized testicular transferrin molecules which can deliver it to specific receptors on the germinal cell surface (Huggenvik et al., 1984). Functionally, all of the secreted proteins from Sertoli cells which have been characterized or proposed fall into one of five basic classes. First, Sertoli cells secrete a number of transport proteins including transferrin, ceruloplasmin, and ABP. The proposed function of these proteins is the transport of Fe3+, Cu2+, and androgens to the germinal cells or to the epididymis (ABP). Second, Sertoli cells synthesize and secrete a number of proteins which have a hormone-like or growth factor-like activity. AMH is a clear and well-documented example of this type of product while the evidence for inhibin, somatomedin C, EGF-like growth factor, and seminiferous growth factor will require further corroboration. Third, Sertoli cells secrete proteins which have enzymatic activities. Plasminogen activator is the best characterized example of this class of products and the alpha-lactalbumin-like activity is of potential interest. The fourth class of Sertoli cell secretion products includes those proteins which contribute to the basement membrane, namely, type IV collagen and laminin. Finally, there is a very important group of Sertoli cell secretion products for which there is, as yet, no evidence for a defined function. This group includes SGP-1 and SGP-2 which are the major sertoli cell products in rats and which have been well-characterized biochemically.(ABSTRACT TRUNCATED AT 400 WORDS)
如引言中所述，支持细胞的许多功能显然是由这些细胞的蛋白质分泌物来执行的。使用支持细胞培养以及适当的生化和免疫技术，已能够对其中一些分泌产物进行表征。由于血睾屏障的存在，支持细胞的许多功能可能是必需的。大多数细胞可通过血清获得细胞存活所需的许多生长和营养因子。近腔室中的生殖细胞无法接触血清因子，支持细胞的功能之一是合成血清样成分并将其分泌到近腔室中。因此，将支持细胞历史上描述为“滋养细胞”似乎是准确的。滋养细胞的功能最清楚地体现在所提出的生殖细胞获取铁离子的机制中。支持细胞已形成一种系统，可使血清来源的铁穿过其自身的细胞质，并将其与新合成的睾丸转铁蛋白分子结合后分泌出来，这些分子可将铁传递至生殖细胞表面的特定受体（胡根维克等人，1984年）。在功能上，已表征或提出的支持细胞分泌的所有蛋白质可分为五个基本类别之一。首先，支持细胞分泌多种转运蛋白，包括转铁蛋白、铜蓝蛋白和雄激素结合蛋白（ABP）。这些蛋白质的推测功能是将Fe3+、Cu2+和雄激素转运至生殖细胞或附睾（ABP）。其次，支持细胞合成并分泌多种具有激素样或生长因子样活性的蛋白质。抗苗勒管激素（AMH）是这类产物的一个明确且有充分文献记载的例子，而抑制素、生长激素介质C、表皮生长因子样生长因子和生精生长因子的证据还需要进一步证实。第三，支持细胞分泌具有酶活性的蛋白质。纤溶酶原激活剂是这类产物中表征最清楚的例子，α-乳白蛋白样活性也具有潜在意义。支持细胞分泌产物的第四类包括那些有助于形成基底膜的蛋白质，即IV型胶原和层粘连蛋白。最后，有一组非常重要的支持细胞分泌产物，目前尚无明确功能的证据。这组产物包括大鼠中主要的支持细胞产物SGP-1和SGP-2，它们在生化方面已得到充分表征。（摘要截于400字）
