EXPRESSION OF P-GLYCOPROTEIN (P-gp/Mdr1/Abcb1) IN RAT LIVER, KIDNEYS, AND GASTROINTESTINAL TRACT ; DISTRIBUTION AND SEX DIFFERENCES

P-gp is an ATP-dependent transmembrane efflux transporter constitutively expressed in the liver bile canaliculi (BC), renal proximal tubules (PT), intestinal epithelium, blood-tissue barriers, maternal-fetal barriers, and hematopoietic cells. In the BC, the P-gp expression exhibits sex differences (males (M)M) in the P-gp expression in BC ; gonadectomy in M, but not in F increased this expression. In the kidneys, the antibody stained the PT brush-border membrane ; gonadectomy in M, but not in F, decreased this expression in the cortex and increased in the outer stripe. In the intestine, the P-gp expression increased from proximal to distal segments, but sex differences or effects of gonadectomy were not observed. The data indicate that in rats, androgens inhibit the expression of P-gp in BC and PT S3 segments, and stimulate in the PT S2 segments.