Mesenteric lymph from rats with thermal injury prolongs the action potential and increases Ca2+ transient in rat ventricular myocytes.
Although gut-derived mesenteric lymph from animals with thermal injury appears to lead to myocardial contractile dysfunction, the cellular mechanisms remain unclear. We examined the direct effects of intestinal lymph on excitation-contraction coupling in rat ventricular myocytes. Lymph from rats receiving burn injury (burn lymph), but not from sham-burned rats, rapidly enhanced myocyte contraction and the amplitude of Ca2+ transient; the average percentage of shortening was increased from 5.5 +/- 0.3% to 10.5 +/- 0.9%. 90% and the Ca2+ transients increased by 80% +/- 20%. Burn lymph had no effect on the amplitude of L-type Ca2+ current (ICa) or the inward rectifier K+ current, but the transient outward K+ currents (Ito) were reduced significantly by burn lymph. Inhibition of Ito was not altered by an alpha1-adrenergic receptor (AR) antagonist, prazosin, indicating that the block was not mediated via alpha1-AR signaling pathway. Action potential (AP) duration, measured at 50% and 90% repolarization, was prolonged by burn lymph. Stimulation of myocytes with AP voltage-clamp waveforms derived from prolonged AP induced by burn lymph revealed a 1.7-fold increase in Ca2+ influx via ICa compared with the Ca2+ influx induced by control AP. Blocking of Ito by 4-aminopyridine prolonged AP duration and increased Ca2+ transients, mimicking the effects of burn lymph. Burn lymph did not affect Na+/Ca2+ exchange currents or caffeine-induced SR Ca2+ release. Thus, acute exposure of normal cardiac myocytes to burn lymph increases Ca2+ transients by a prolongation of AP as a result of a reduction of Ito with no intrinsic change in ICa or exchanger. The electrophysiological changes are similar to those that occur during compensated cardiac hypertrophy, suggesting a common mechanistic link between burn lymph- and hypertrophy-induced cardiac dysfunction.
Yatani
Atsuko
A
Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, New Jersey 07101-1709, USA. yataniat@umdnj.edu
Xu
Da-Zhong
DZ
Kim
Song-Jung
SJ
Vatner
Stephen F
SF
Deitch
Edwin A
EA
D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002056:Burns / Q000503:physiopathology*; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020747:Calcium Channels, T-Type / Q000187:drug effects / Q000502:physiology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004594:Electrophysiology; D008094:Lithium / Q000494:pharmacology; D008196:Lymph / Q000502:physiology*; D008297:Male; D008643:Mesentery / Q000503:physiopathology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000737:chemistry / Q000502:physiology; D019831:Sodium-Calcium Exchanger / Q000187:drug effects / Q000502:physiology
D020747:Calcium Channels, T-Type; D015221:Potassium Channels; D019831:Sodium-Calcium Exchanger; D002110:Caffeine; D004533:Egtazic Acid; D008094:Lithium; D015761:4-Aminopyridine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D011188:Potassium; D002118:Calcium