Cavazzini D, Galdieri M, Ottonello S
Institute of Biochemical Sciences, University of Parma, Italy.
Biochim Biophys Acta. 1996 Aug 28;1313(2):139-45. doi: 10.1016/0167-4889(96)00065-1.
At physiological plasma concentrations, retinoic acid (RA) cannot cross the blood-testis barrier formed by Sertoli and peritubular cells, and it is thought to be mainly synthesized in situ through the oxidation of retinol. We have thus examined the in vitro RA biosynthetic capacity of cultured Sertoli and peritubular cells isolated from the seminiferous tubules of prepubertal rats, using holo-cellular retinol binding protein (CRBP) as a substrate. Although both somatic cell types contain CRBP and retinoic acid nuclear receptors, RA synthesis was only detected with Sertoli cell subcellular fractions. Most of the RA synthesizing activity of these cells is contributed by a microsomal-cytosolic system that shares many functional similarities with a RA biosynthetic pathway originally identified in rat liver. RA synthesis is maximal at a time of postnatal life (20 days) preceding meiotic cell accumulation and remains nearly constant thereafter. The unique ability of Sertoli cell subcellular fractions to support RA formation from holoCRBP, along with the observed age-dependent modulation of this activity, indicate that Sertoli cells represent the main site of intratubular RA production and that they may play a key role in controlling RA-dependent processes within the seminiferous tubule.
在生理血浆浓度下，视黄酸（RA）无法穿过由支持细胞和睾丸周细胞形成的血睾屏障，人们认为它主要通过视黄醇的氧化在原位合成。因此，我们使用全细胞视黄醇结合蛋白（CRBP）作为底物，检测了从青春期前大鼠的生精小管中分离出的培养支持细胞和睾丸周细胞的体外RA生物合成能力。尽管这两种体细胞类型都含有CRBP和视黄酸核受体，但仅在支持细胞亚细胞组分中检测到RA合成。这些细胞的大部分RA合成活性由一个微粒体-胞质系统贡献，该系统与最初在大鼠肝脏中鉴定出的RA生物合成途径具有许多功能相似性。RA合成在减数分裂细胞积累之前的出生后时期（20天）达到最大值，此后几乎保持恒定。支持细胞亚细胞组分从全CRBP支持RA形成的独特能力，以及观察到的这种活性的年龄依赖性调节，表明支持细胞是管内RA产生的主要部位，并且它们可能在控制生精小管内依赖RA的过程中起关键作用。
