Format

Send to

Choose Destination
See comment in PubMed Commons below
Circ Res. 2011 Apr 15;108(8):971-9. doi: 10.1161/CIRCRESAHA.110.238386. Epub 2011 Feb 24.

Small-conductance calcium-activated potassium channel and recurrent ventricular fibrillation in failing rabbit ventricles.

Author information

1
Krannert Institute of Cardiology, Division of Cardiology, Indiana University School of Medicine, Indianapolis, USA.

Abstract

RATIONALE:

Fibrillation/defibrillation episodes in failing ventricles may be followed by action potential duration (APD) shortening and recurrent spontaneous ventricular fibrillation (SVF).

OBJECTIVE:

We hypothesized that activation of apamin-sensitive small-conductance Ca(2+)-activated K(+) (SK) channels is responsible for the postshock APD shortening in failing ventricles.

METHODS AND RESULTS:

A rabbit model of tachycardia-induced heart failure was used. Simultaneous optical mapping of intracellular Ca(2+) and membrane potential (V(m)) was performed in failing and nonfailing ventricles. Three failing ventricles developed SVF (SVF group); 9 did not (no-SVF group). None of the 10 nonfailing ventricles developed SVF. Increased pacing rate and duration augmented the magnitude of APD shortening. Apamin (1 μmol/L) eliminated recurrent SVF and increased postshock APD(80) in the SVF group from 126±5 to 153±4 ms (P<0.05) and from 147±2 to 162±3 ms (P<0.05) in the no-SVF group but did not change APD(80) in nonfailing group. Whole cell patch-clamp studies at 36°C showed that the apamin-sensitive K(+) current (I(KAS)) density was significantly larger in the failing than in the normal ventricular epicardial myocytes, and epicardial I(KAS) density was significantly higher than midmyocardial and endocardial myocytes. Steady-state Ca(2+) response of I(KAS) was leftward-shifted in the failing cells compared with the normal control cells, indicating increased Ca(2+) sensitivity of I(KAS) in failing ventricles. The K(d) was 232±5 nmol/L for failing myocytes and 553±78 nmol/L for normal myocytes (P=0.002).

CONCLUSIONS:

Heart failure heterogeneously increases the sensitivity of I(KAS) to intracellular Ca(2+), leading to upregulation of I(KAS), postshock APD shortening, and recurrent SVF.

PMID:
21350217
PMCID:
PMC3086382
DOI:
10.1161/CIRCRESAHA.110.238386
[Indexed for MEDLINE]
Free PMC Article

Publication types, MeSH terms, Substances, Grant support

Publication types

MeSH terms

Substances

Grant support

PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Support Center