Korean J Physiol Pharmacol.  1999 Dec;3(6):623-630.

Depression of L-type Ca2+ and transient outward K+ currents in endotoxin-treated rat cardiac myocytes

• Park KS
• Lee BS
• Kong ID
• Lee JW

Abstract

Decreased cardiac contractility occurs in endotoxicosis, but little is known about the ionic mechanism responsible for myocardial dysfunction. In this study, we examined the changes in Ca2+ and K+ currents in cardiac myocytes from endotoxin-treated rat. Ventricular myocytes were isolated from normal and endotoxemic rats (ex vivo), that were treated for 10 hours with Salmonella enteritidis lipopolysaccharides (LPS; 1.5 mg/kg) intravenously. Normal cardiac myocytes were also incubated for 6 hours with 200 ng/ml LPS (in vitro). L-type Ca2+ current (ICa,L) and transient outward K+ current (Ito) were measured using whole cell patch clamp techniques. Peak ICa,L was reduced in endotoxemic myocytes (ex vivo; 6.00.4 pA/pF, P<0.01) compared to normal myocytes (control; 10.90.6 pA/pF). Exposure to endotoxin in vitro also attenuated ICa,L (8.40.4 pA/pF, P<0.01). The amplitude of Ito on depolarization to 60 mV was reduced in endotoxin treated myocytes (16.51.5 pA/pF, P<0.01, ex vivo; 20.00.9 pA/pF, P<0.01, in vitro) compared to normal myocytes (control; 24.71.0 pA/pF). There was no voltage shift in steady-state inactivation of ICa,L and Ito between groups. These results suggest that endotoxin reduces Ca2+ and K+ currents of rat cardiac myocytes, which may lead to cardiac dysfunction.

Keyword

Endotoxin; Cardiac myocyte; Ca2+ current, K+ current

MeSH Terms

Animals
Depression*
Lipopolysaccharides
Muscle Cells
Myocytes, Cardiac*
Patch-Clamp Techniques
Rats*
Salmonella enteritidis
Lipopolysaccharides