Effects of papaverine and its interaction with isoprenaline and carbachol on the contractile force and cyclic nucleotide levels of the canine ventricular myocardium

1979 ◽  
Vol 306 (3) ◽  
pp. 241-248 ◽  
Author(s):  
M. Endoh ◽  
M. Honma
Keyword(s):  
Cyclic Nucleotide ◽  
Ventricular Myocardium ◽  
Contractile Force ◽  
Canine Ventricular Myocardium

Demonstration of hysteresis in refractoriness of canine ventricular myocardium

1988 ◽  
Vol 255 (6) ◽  
pp. H1342-H1348
Author(s):  
C. Giorgi ◽  
M. Vermeulen ◽  
R. Cardinal ◽  
P. Savard ◽  
R. Nadeau ◽  
...  
Keyword(s):  
Pulse Width ◽  
Cycle Length ◽  
Ventricular Myocardium ◽  
Ventricular Muscle ◽  
Cycle Lengths ◽  
Long Pulse ◽  
Basic Cycle Length ◽  
Canine Ventricular Myocardium

The properties and determinants of hysteresis during ventricular effective refractory period (VERP) measurements by an extrastimulus technique were determined in 15 anesthetized open-chest dogs as well as in isolated ventricular muscle (n = 6). VERP was determined both by decreasing the S1-S2 interval and also by increasing S1S2. Hysteresis was then calculated by subtracting the VERP obtained with the decreasing S1S2 from the VERP obtained with the increasing S1S2. The effects of basic cycle length, pulse width, stimulation intensity, and the number of basic drives on VERP and hysteresis were evaluated. VERP was shorter for long pulse width, high stimulation intensities, and shorter basic cycle lengths. These modifications were not associated with significant changes of hysteresis. VERP was shorter during decreasing S1S2 than during increasing S1S2. Hysteresis was greater with 6 basic drive cycles than with 12 (P less than 0.001) in both in vivo and in vitro preparations. The data suggest that 1) hysteresis occurs during VERP measurements; 2) hysteresis is independent of stimulation modality; and 3) hysteresis decreases with the number of basic drive cycles.

Ca2+ sensitizer Org-30029 reverses acidosis- and BDM-induced contractile depression in canine myocardium

1996 ◽  
Vol 271 (5) ◽  
pp. H1829-H1839 ◽  
Author(s):  
A. Watanabe ◽  
H. Tomoike ◽  
M. Endoh
Keyword(s):  
Direct Action ◽  
Ventricular Myocardium ◽  
Cross Bridge ◽  
Force Relation ◽  
Myocardial Contractile ◽  
Butanedione Monoxime ◽  
The Cross ◽  
Sensitizing Effect ◽  
Canine Myocardium ◽  
Canine Ventricular Myocardium

Effects of the Ca2+ sensitizer N-hydroxy-5,6-dimethoxy-benzo[b]thiophene-2-carboximidamide hydrochloride (Org-30029) on the myocardial contractile depression induced by acidosis and 2,3-butanedione monoxime (BDM) were investigated in aequorin-loaded canine ventricular myocardium. The peak Ca2+ transient-peak force relation during administration of Org-30029 (10(-4) to 10(-3) M) was shifted to the left and upward compared with the relation for elevation of the extracellular Ca2+ concentration ([Ca2+]o) (2.5-12.5 mM). Acidosis (pH 6.6) depressed the force with a small increase in the peak Ca2+ transient. BDM (3 mM) depressed the force with no change in the peak and duration of the Ca2+ transient, indicating that BDM may inhibit selectively the cross-bridge interaction. During acidosis or in the presence of BDM, elevation of [Ca2+]o increased the peak Ca2+ transient to the same extent as that in the control, but the force was inhibited. In contrast, Org-30029 increased the force to a level equivalent to the control with a slight change in the peak Ca2+ transient. In addition, during acidosis, Org-30029 (10(-3) M) increased the force in association with a slight decrease in the peak Ca2+ transient. Thus Org-30029 can reverse the myocardial contractile depression induced by a decrease in the Ca2+ sensitivity of myofilaments, as occurs in pathophysiological situations such as acidosis in cardiac ischemia. Org-30029 may exert the Ca(2+)-sensitizing effect by an increase in the affinity of troponin C for Ca2+ and by a direct action on the cross-bridge interaction.

scholarly journals Analysis of the contribution of Ito to repolarization in canine ventricular myocardium

2011 ◽  
Vol 164 (1) ◽  
pp. 93-105 ◽  
Author(s):  
L Virág ◽  
N Jost ◽  
R Papp ◽  
I Koncz ◽  
A Kristóf ◽  
...  
Keyword(s):  
Ventricular Myocardium ◽  
Canine Ventricular Myocardium
Sign in / Sign up

Export Citation Format

Share Document