P‐glycoprotein in intestines, liver, kidney and lymphocytes in horse

Abstract

P-glycoprotein (P-gp) is an important drug transporter, which is expressed in a variety of cells, such as the intestinal enterocytes, the hepatocytes, the renal tubular cells and the intestinal and peripheral blood lymphocytes. We have studied the localization and the gene and protein expression of P-gp in these cells in horse. In addition we have compared the protein sequence of P-gp in horse with the protein sequences of P-gp in several other species. Real time RT-PCR and Western blot showed gene and protein expression of horse P-gp in all parts of the intestines, but there was no strict correlation between these parameters. Immunohistochemistry showed localization of P-gp in the apical cell membranes of the enterocytes and, in addition, staining was observed in the intestinal intraepithelial and lamina propria lymphocytes. Peripheral blood lymphocytes also stained for P-gp, and gene and protein expression of P-gp were observed in these cells. There was a high gene and protein expression of P-gp in the liver, with P-gp-immunoreactivity in the bile canalicular membranes of the hepatocytes. Gene and protein expression of P-gp were found in the kidney with localization of the protein in different parts of the nephrons. Protein sequence alignment showed that horse P-gp has two amino acid insertions at the N-terminal region of the protein, which are not present in several other species examined. One of these is a 99 amino acid long sequence inserted at amino acid positions 23-121 from the N-terminal. The other is a six amino acid long sequence present at the amino acid positions 140-145 from the N-terminal. The results of the present study indicate that P-gp has an important function for oral bioavailability, distribution and excretion of substrate compounds in horse.

PGP expression in Cooperia oncophora before and after ivermectin selection

“…The 25-μl RT-PCR reactions contained 12.5 μl 2× QIAGEN Quanti Tect SYBR Green master mix, 0.5 μl Forward primer (10 μM), 0.5 μl reverse primer (10 μM), 0.25 μl Q-RT, 1.25 μl of RNAse-free H 2 O and 10 μl RNA sample adjusted to contain 2 ng total RNA from each single worm. Thus, PGP expression was normalised to the amount of total RNA in the PCR reaction as previously described by Tyden et al (2009). All samples were run in technical duplicates.…”

Expression and localization of BCRP, MRP1 and MRP2 in intestines, liver and kidney in horse

“…Total RNA was prepared with NucleoSpin RNA II kit containing DnaseI (Macherey‐Nagel) following the instructions from the manufacturer. The purity and integrity of the RNA was checked as described previously (Tydén et al. , 2009).…”

“…We have recently examined the gene and protein expression and the cellular localization of P‐gp in the intestines, liver and kidney in horse (Tydén et al. , 2009).…”

Oral Absorption of Clarithromycin Is Nearly Abolished by Chronic Comedication of Rifampicin in Foals

“…Hence, alternative intestinal absorption pathways that are susceptible to inhibition by RIF must exist. In any case, in assuming competition of RIF with an intestinal uptake transporter for CLR, it must be considered that RIF also modulates ABCB1 and ABCC2 (Zong and Pollack, 2003;Lau et al, 2006), which are also expressed in the horse intestine (Tydén et al, 2009). Thus, the net effect resulting from modulation of intestinal OATP(s) and/or induction of ABCB1/ABCC2 must have overshadowed the extent of the modulating effects of RIF on the ABCB1/ABCC2-mediated efflux of CLR.…”