| Abstract | Glikoprotein P (P-gp) je o ATP-u ovisan membranski prijenosnik lijekova i drugih tvari (MDR1 eng. Multi Drug Resistant protein 1) izražen u kanalikularnoj membrani jetrenih stanica, četkastoj membrani bubrežnih proksimalnih kanalića (PK), epitelnim stanicama crijeva, krvno-moždanoj, materno-fetalnoj barijeri te u hematopoetskim stanicama. Spolni hormoni utječu na ekspresiju P-gp u jetri štakora (mužjaci (M) > ženki (Ž)), ali hormon/i odgovorni za te razlike, kao i moguće spolne razlike u drugim organima nisu podrobno istraženi. U ovom radu istraženi su: ekspresija, spolne razlike te učinci gonadektomije i obrade spolnim hormonima gonadektomiranih životinja na ekspresiju P-gp u jetri, bubrezima i probavnom traktu muških i ženskih štakora soja Wistar metodama imunocitokemije i Western analize. Dodatno, istražene su dobne razlike u ekspresiji P-gp u jetri i bubrezima novorođenih (1 dan starosti), predpubertetskih (3 tjedna starosti), odraslih (3 mjeseca starosti) i ostarjelih (2 godine starosti) životinja. Ovim radom potvrdili smo spolne razlike u ekspresiji P-gp (M < Ž) u jetri i pokazali da kastracija ima stimulacijski učinak, dok tretman kastrata estradiolom nije imao značajan utjecaj na ekspresiju P-gp, što ukazuje na androgene kao glavne regulatore (inhibitore) jetrene ekspresije P-gp. U bubrezima, spolne razlike nađene su u kori (S1/S2 segmenti PK; M > Ž)) i vanjskom tračku (S3 segmenti PK; M < Ž). U bubrezima ženskih štakora, gonadektomija je smanjila, dok u muških štakora nije imala učinka na ekspresiju P-gp. Tretman kastrata estradiolom smanjio je ekspresiju P-gp u kori i povećao u vanjskom tračku, ukazujući na estrogene kao glavne regulatore ekspresije P-gp u bubrezima. U crijevima, utvrđena je ekspresija P-gp po obrascu: V duodenum < jejunum < ileum > cekum > kolon). Spolne razlike nađene su u duodenumu, jejunumu, ileumu i kolonu (M < Ž) te u cekumu (M > Ž); učinak gonadektomije nije uočen zbog velike varijabilnosti rezultata. Dobne razlike u ekspresija P-gp uočene su u jetri (novorođeni > prepubertetski > odrasli < stari) i bubrezima (novorođeni < prepubertetski < odrasli > stari). Postojanje spolnih i dobnih razlika u ekspresiji P-gp u glavnim (re)apsorpcijskim i sekrecijskim organima u štakora ukazuje na heterogenost njihovih zadaća, što može bitno utjecati na procjenu obima transporta, međudjelovanja i toksičnosti različitih lijekova i drugih ksenobiotika, te nastanak rezistencije na lijekove u ovih pokusnih životinja, važnim u eksperimentalnim i pretkliničkim/translacijskim istraživanjima. |
| Abstract (english) | P-glycoprotein (P-gp) is an ATP-dependent transmembrane multidrug efflux transporter (MDR1) constitutively expressed in the hepatocyte bile canaliculi, renal proximal tubule (PT) brush border membrane, intestinal epithelium, blood-tissue barriers, maternal-fetal barriers, and hematopoietic cells. It is known that sex steroids influence the P-gp expression in rat liver (males (M) > females (F)), but hormone(s) responsible for these differences, and possible sex differences in other P-gp expressing organs, have not been investigated in detail. In this study the expression, sex differences, effects of gonadectomy, and treatment with sex steroids on the expression of P-gp in liver, kidneys, and gastrointestinal tract of M and F Wistar rats were investigated by immunocytochemistry and Western blotting. Additionally, age-differences in P-gp expression in liver and kidneys of neonatal (age of 1 day), prepubertal (age of 3 weeks), adult (age of 3 months), and old (age of 2 years) animals were investigated. In liver, we confirmed sex differences in P-gp expression (M < F), and showed that castration stimulated, while estradiol treatment did not significantly affect the P-gp expression in castrated M. Thus indicating androgens as major regulators (inhibitors) of the liver P-gp expression. In kidneys, sex differences were found in cortex (PT S1/S2 segments; M > F)) and outer stripe (PT S3 segments; M < F). Gonadectomy decreased the P-gp expression in F, without effecting the expression in M. Estradiol treatment decreased the P-gp expression in cortex and increased expression in outer stripe in castrated M, thus indicating estrogens as major regulators of the renal P-gp expression. In intestine, the following pattern of P-gp expression was identified: duodenum < jejunum < VII ileum > cecum > colon). Sex differences were detected in duodenum, jejunum, ileum and colon (M < F), and in cecum (M > F); an effect of gonadectomy was not detected due to high variability of results. Age differences in P-gp expression were found in liver (neonatal > prepubertal > adult < old) and in kidneys (neonatal < prepubertal < adult > old). The presence of sex and age differences in P-gp expression in major (re)absorptive and secretory organs in rats indicates heterogeneity of their functions, which may affect evaluations of the transport, interactions and toxicity of various drugs and other xenobiotic, and development of drug resistance in these animals, important in experimental and preclinical/translational studies. |
