Xenobiotic and Endobiotic Transporter Mrna Expression in the Blood-Testis Barrier

Abstract

ABSTRACT:A major function of xenobiotic and endobiotic transporters is to move a wide range of organic substances across cell membranes. Sertoli cells play an important role in protecting developing germ cells by forming a physiological barrier, limiting exposure to potentially toxic substrates, or conversely, facilitating uptake of xenobiotics within the testis. The aim of this study was to quantitatively determine the constitutive expression of various transporters in isolated Sertoli cells from adult Sprague-Dawley rats. The following mRNA levels were measured in isolated Sertoli cells by the branched DNA signal amplification method, multidrug resistance (Mdr) protein 1a, 1b, and 2; multiple drug resistance protein (Mrp) 1, 2, 3, 4, 5, 6, 7, and 8; sodium taurocholate cotransporting polypeptide; bile salt excretory protein; ileal bile acid transporter; AbcG5 and AbcG8; organic anion transporting polypeptide (Oatp) 1, 2, 3, 4, 5, 9, and 12; prostaglandin transporter (Pgt); testisspecific transporter (Tst) 1 and Tst2; organic anion transporter (Oat) 1, 2, 3, and K; organic cation transporter (Oct) 1, 2, 3, N1, and N2; divalent metal transporter (Dmt) 1, Menke's, and Wilson's; zinc transporter (Znt) 1; equilibrative nucleoside transporter (Ent) 1 and 2; concentrative nucleoside transporter (Cnt) 1 and 2; and peptide transporter (Pept) 1 and 2. Levels were also determined in whole testis, liver, kidney, and ileum to provide a reference for determining relative expression levels. Mrp8, Tst1 and 2, and Ent1 and 2 were expressed in Sertoli cells at higher levels than in liver, kidney, or ileum, whereas Mrp1, 5, and 7, Mdr2, Oatp3, Oat2, OctN2, Dmt1, Menke's, Wilson's, and Znt1 were all significantly expressed in Sertoli cells, but Sertoli cell expression was not the tissue of highest expression. The remaining transporters were expressed at low levels in isolated Sertoli cells. Additionally, expression levels of Mrp1, Mrp7, Mrp8, Tst1, Tst2, OctN2, Wilson's, Znt1, Ent1, and Ent2 were greater in isolated Sertoli cells than in whole testis. Constitutive expression of transporters in Sertoli cells may provide an insight into the range of xenobiotics that can potentially be transported by Sertoli cells and thereby provide a mechanistic understanding of blood-testis barrier function.

Isolation and Characterization of Polyspecific Mouse Organic Solute Carrier Protein 1 (mOscp1)

“…This barrier function, the blood-testis barrier, mediates the absorption and excretion of essential nutrients and organic solutes and provides protection from toxic compounds (Russell, 1977). Recently, expression of several organic ion transporters such as multiple drug resistance proteins, multidrug resistance proteins, Oatps, OCTs, carnitine transporter 2 (CT2), and gonad-specific transporter 1 and 2 (GST-1/2) have been demonstrated in the testis (Enomoto et al, 2002;Suzuki et al, 2003;Augustine et al, 2005). The role of these transporters is to facilitate the supply of water-soluble compounds and to protect the reproductive system.…”

Expression of Thirty-six Drug Transporter Genes in Human Intestine, Liver, Kidney, and Organotypic Cell Lines

“…Quantitative gene expression data from rat ileum, liver, and kidney have been published recently (Augustine et al, 2005). This analysis covered more than 30 transporter genes, 20 of which were orthologs to the genes in our analysis.…”

“…Our final aim was to compare our data with recently published data from rat tissue, to obtain information on species differences in transporter expression profiles. This comparison was motivated by the fact that the rat is the most commonly used species in preclinical drug discovery pharmacokinetic studies and because there are numerous examples of discrepancies between humans and rats in this context (Augustine et al, 2005).…”

ABCC10, ABCC11, and ABCC12

“…A murine homologue of MRP9 has been reported (85% identical to MRP9; 48% identical to MRP8), whereas an orthologue of MRP8 is absent from the mouse genome [21]. Mrp9 transcript is abundantly expressed in testis, with very modest expression in other tissues [12,14]. In testis, the transcript has been localized to sertoli cells of the seminiferous tubules, with lower levels in leydig cells.…”

“…Murine Mrp7 is ∼84% identical to MRP7, and its transcript is expressed in many tissues, with highest levels in testis, ovary, gut, kidney, and lung [12,13]. Rat Mrp7 transcript was reported to be expressed in liver, kidney, and ileum [14]. MRP8 and MRP9 are closely related proteins (47% identity) whose genes are located in close proximity and in a head to tail orientation at 16q12 [15][16][17].…”