Chronic nifedipine treatment diminishes cardiac inotropic response to nifedifine: Functional upregulation of dihydropyridine receptors

Gladys E. Chiappe de Cingolani, Susana M. Mosca, Abel E. Moreyra, Horacio E. Cingolani

Research output: Contribution to journalArticlepeer-review

Abstract

Chronic treatment with nifedipine induces up-regulation of functional active Ca2+ channels in cardiac muscle membranes. Adult male New Zealand White rabbits (NZW) were treated with nifedipine (20 mg/day) for 25 days. In isovolumic perfused hearts at constant coronary flow and heart rate (HR) the left ventricular developed pressure (LVDP) and its first derivative (dP/dt) were monitored. Basal contractility and contractility at different end- diastolic volumes (EDV) were higher in nifedipine-treated animals, with no changes in diastolic chamber stiffness. Dose response to nifedipine in pretreated animals showed less decrease in contractility than in controls [ED50 = 1.09 ± 0.09 x 10-7 (control) and 1.55 ± 0.17 x 10-7 M nifedipine (treated) (p < 0.05)]. Ca2+ channel density was assessed by specific binding at the dihydropyridine receptor with [methyl-3H]PN 200- 110. In cardiac membranes, maximal binding capacity (B(max)) was 269 ± 38 (n = 7, control) and 429 ± 46 fmol/mg protein (n = 7, treated) (p < 0.05), without significant changes in dissociation constant. In addition, we noted no changes in dihydropyridine (DHP) binding sites in aortic membranes. Our results offer a possible explanation for the lack of decrease in contractility despite the persistent hypotensive effect in hypertensive patients during chronic treatment with nifedipine.

Original languageEnglish (US)
Pages (from-to)240-246
Number of pages7
JournalJournal of cardiovascular pharmacology
Volume27
Issue number2
DOIs
StatePublished - Feb 12 1996

Keywords

  • Calcium channels
  • Dihydropyridine receptors
  • Heart contractility
  • Nifedipine treatment

ASJC Scopus subject areas

  • Pharmacology
  • Cardiology and Cardiovascular Medicine

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