Measuring MDR-1 by Quantitative RT-PCR

St John's wort modulation and developmental expression of multidrug transporters in the rat

Extracts of St John's wort (SJW) (Hypericum perforatum) are a potent inducer of enzymes of the cytochrome P450 system and of the transport protein P-glycoprotein, and interactions with a range of commonly prescribed medications have been described. In addition, recent experimental data suggest that, this otherwise safe treatment, could have some side effects when consumed during pregnancy and lactation. The aim of this study was to investigate, in Wistar rats, the effect of a treatment with high doses of SJW extract (100 and 1000 mg/kg/day) administered prenatally and during breastfeeding, on the level of transcripts of mdr1a, mdr1b, mrp1, mrp2 and cyp3A2 genes. All transcripts were detected in the liver, and their level of expression increased from fetuses to adults. SJW administration, at both dosages, caused a significant decrease of the levels of mdr1a, mdr1b, mrp1 and mrp2 in the livers of fetuses, and an increase in the levels of mdr1a, mdr1b, mrp2 and cyp3A2 in the mothers. In the other organs examined, a physiological regulation during ontogenesis was also evident, but SJW administration did not modify the expression level of the considered transcripts. These data suggest that the administration of the extract together with drugs that are substrates of transport proteins could be particularly hazardous during pregnancy.

Physiological regulation of P-glycoprotein, MRP1, MRP2 and cytochrome P450 3A2 during rat ontogeny

P-glycoprotein and the multidrug resistance-related proteins MRP1 and MRP2 belong to the ATP binding cassette family of proteins and transport a wide range of substrates. These proteins are also involved in metabolic and excretory processes of xenobiotics. The rat genes mdr1a and mdr1b code for P-glycoproteins, while mrp1 and mrp2 genes code for MRP1 and MRP2 proteins, respectively. In this study, the physiological modulation of the level of transcript for these genes during rat ontogeny in the liver, kidney, lung, brain and heart was analyzed by reverse transcription-polymerase chain reaction. An increasing level of transcript during ontogeny was demonstrated for mdr1a and mdr1b in all tissues considered, as well as for mrp2, which was detected only in the liver and kidney. In contrast, mrp1 transcript, present in all tissues, did not show any modulation. The maximum level of expression was reached in adult animals and a significant decrease was demonstrated in aging rats. Western blot analysis with C219 and M2III-6 monoclonal antibodies confirmed this different pattern of expression during ontogeny in the liver. The physiological regulation of cytochrome P450 3A2 was also considered: in the rat liver, an increase in the level of transcript during ontogeny, with a maximum in 60-day-old rats and a decrease in 8-month-old rats, was evident.