title: Tachycardia-induced heart failure does not alter myocardial P-glycoprotein expression.
abstract: OBJECTIVE
  To determine the effects of tachycardia-induced heart failure on myocardial P-glycoprotein (P-gp) expression.
  
  
  METHODS
  Nonblinded, parallel, sham-controlled, animal model study.
  
  
  METHODS
  University laboratory.
  
  
  METHODS
  Thirty mongrel dogs.
  
  
  METHODS
  Heart failure was induced by rapid ventricular pacing over 4 weeks; sham procedures were performed for the control group.
  
  
  RESULTS
  Myocardial biopsies were taken from the left ventricular lateral wall and prepared for P-gp quantification by laser-induced fluorescence. The relative amount of P-gp messenger RNA (mRNA) was assessed by reverse transcriptase polymerase chain reaction. Rapid ventricular pacing produced heart failure and reduced the area ejection fraction from 48% +/- 6% to 21% +/- 6% (p<0.05 vs baseline). However, heart failure did not alter the quantity of myocardial P-gp (0.20 +/- 0.02 microg/ml for the control group vs 0.23 +/- 0.02 microg/ml for the intervention group, p=0.4). Furthermore, heart failure did not alter P-gp expression significantly.
  
  
  CONCLUSIONS
  Myocardial P-gp does not change in response to tachycardia-induced heart failure. Thus, there is a low likelihood for P-gp-related drug resistance during a syndrome similar to tachycardia-induced heart failure.
authors.affiliation: University of Wisconsin-Madison School of Pharmacy, Madison, Wisconsin 53705, USA. jjsims@pharmacy.wisc.edu
authors.forename: J Jason
authors.initials: JJ
authors.lastname: Sims
authors.forename: Brien L
authors.initials: BL
authors.lastname: Neudeck
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Loeb
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Wiegert
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002311:Cardiomyopathy, Dilated / Q000209:etiology* / Q000503:physiopathology; D004285:Dogs; D004452:Echocardiography; D020869:Gene Expression Profiling; D006023:Glycoproteins / Q000737:chemistry* / Q000502:physiology; D006352:Heart Ventricles / Q000737:chemistry* / Q000601:surgery; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013610:Tachycardia / Q000150:complications* / Q000503:physiopathology; D013997:Time Factors
chemical_list: D006023:Glycoproteins