Department of Pharmacology & Toxicology, College of Pharmacy (R.K.H., N.J.C.), and Departments of Pathology (R.R.K.) and Physiology (S.H.W.), College of Medicine, University of Arizona, Tucson, Arizona.
Department of Pharmacology & Toxicology, College of Pharmacy (R.K.H., N.J.C.), and Departments of Pathology (R.R.K.) and Physiology (S.H.W.), College of Medicine, University of Arizona, Tucson, Arizona
Drug Metab Dispos. 2022 Jun;50(6):770-780. doi: 10.1124/dmd.121.000748. Epub 2022 Mar 20.
The blood-testis barrier (BTB) is formed by basal tight junctions between adjacent Sertoli cells (SCs) of the seminiferous tubules and acts as a physical barrier to protect developing germ cells in the adluminal compartment from reproductive toxicants. Xenobiotics, including antivirals, male contraceptives, and cancer chemotherapeutics, are known to cross the BTB, although the mechanisms that permit barrier circumvention are generally unknown. This study used immunohistological staining of human testicular tissue to determine the site of expression for xenobiotic transporters that facilitate transport across the BTB. Organic anion transporter (OAT) 1, OAT2, and organic cation transporter, novel (OCTN) 1 primarily localized to the basal membrane of SCs, whereas OCTN2, multidrug resistance protein (MRP) 3, MRP6, and MRP7 localized to SC basal membranes and peritubular myoid cells (PMCs) surrounding the seminiferous tubules. Concentrative nucleoside transporter (CNT) 2 localized to Leydig cells (LCs), PMCs, and SC apicolateral membranes. Organic cation transporter (OCT) 1, OCT2, and OCT3 mostly localized to PMCs and LCs, although there was minor staining in developing germ cells for OCT3. Organic anion transporting polypeptide (OATP) 1A2, OATP1B1, OATP1B3, OATP2A1, OATP2B1, and OATP3A1-v2 localized to SC basal membranes with diffuse staining for some transporters. Notably, OATP1C1 and OATP4A1 primarily localized to LCs. Positive staining for multidrug and toxin extrusion protein (MATE) 1 was only observed throughout the adluminal compartment. Definitive staining for CNT1, OAT3, MATE2, and OATP6A1 was not observed. The location of these transporters is consistent with their involvement in the movement of xenobiotics across the BTB. Altogether, the localization of these transporters provides insight into the mechanisms of drug disposition across the BTB and will be useful in developing tools to overcome the pharmacokinetic and pharmacodynamic difficulties presented by the BTB. SIGNIFICANCE STATEMENT: Although the total mRNA and protein expression of drug transporters in the testes has been explored, the localization of many transporters at the blood-testis barrier (BTB) has not been determined. This study applied immunohistological staining in human testicular tissues to identify the cellular localization of drug transporters in the testes. The observations made in this study have implications for the development of drugs that can effectively use transporters expressed at the basal membranes of Sertoli cells to bypass the BTB.
血睾屏障（BTB）由相邻生精小管中的 Sertoli 细胞（SCs）之间的基底紧密连接形成，作为物理屏障，保护腔室中的发育中的生殖细胞免受生殖毒物的侵害。已经知道，包括抗病毒药、男性避孕药和癌症化疗药物在内的外源性化学物质可以穿过 BTB，尽管允许屏障规避的机制通常尚不清楚。本研究使用人睾丸组织的免疫组织化学染色来确定促进穿过 BTB 运输的外源性化学物质转运体的表达部位。有机阴离子转运蛋白 (OAT) 1、OAT2 和有机阳离子转运蛋白、新型 (OCTN) 1 主要定位于 SC 的基底膜，而 OCTN2、多药耐药蛋白 (MRP) 3、MRP6 和 MRP7 定位于 SC 的基底膜和围绕生精小管的周细胞（PMCs）。浓缩核苷转运蛋白 (CNT) 2 定位于 Leydig 细胞 (LCs)、PMCs 和 SC 顶端膜。有机阳离子转运蛋白 (OCT) 1、OCT2 和 OCT3 主要定位于 PMCs 和 LCs，但 OCT3 在发育中的生殖细胞中有少量染色。有机阴离子转运多肽 (OATP) 1A2、OATP1B1、OATP1B3、OATP2A1、OATP2B1 和 OATP3A1-v2 定位于 SC 的基底膜，一些转运体呈弥漫性染色。值得注意的是，OATP1C1 和 OATP4A1 主要定位于 LCs。多药和毒素外排蛋白 (MATE) 1 的阳性染色仅在腔室中观察到。未观察到 CNT1、OAT3、MATE2 和 OATP6A1 的明确染色。这些转运体的位置与其参与外源性化学物质穿过 BTB 的运动一致。总之，这些转运体的定位为了解药物穿过 BTB 的分布机制提供了线索，并将有助于开发克服 BTB 带来的药代动力学和药效动力学困难的工具。意义声明：尽管已经探索了睾丸中转录物药物转运体的总 mRNA 和蛋白表达，但许多转运体在血睾屏障（BTB）处的定位尚未确定。本研究在人睾丸组织中应用免疫组织化学染色来确定睾丸中转录物药物转运体的细胞定位。本研究中的观察结果对开发可以有效利用 Sertoli 细胞基底膜表达的转运体来绕过 BTB 的药物具有重要意义。
