Acute Effects of Diuretics on Potassium Exchange, Mechanical Function and the Action Potential in Rabbit Myocardium

1978 ◽  
Vol 55 (6) ◽  
pp. 555-559
Author(s):  
P. A. Poole-Wilson ◽  
S. M. Cobbe ◽  
C. H. Fry
Keyword(s):  
Action Potential ◽  
Interventricular Septum ◽  
Papillary Muscles ◽  
Mechanical Function ◽  
Acute Effects ◽  
Rabbit Myocardium ◽  
Potassium Exchange

1. We have studied the acute effects of frusemide, triamterene and amiloride on potassium exchange, the action potential and mechanical function of isolated rabbit myocardium. 2. Potassium exchange in the myocardium was unaltered by these diuretics. 3. Frusemide and amiloride did not affect the action potential of rabbit papillary muscles. Triamterene caused a transient shortening of the action potential. 4. Frusemide and triamterene did not alter myocardial mechanical function in rabbit papillary muscles or the interventricular septum. Amiloride caused a reduction of about 5% in developed tension in two out of three papillary muscles.

Effects of acidosis on mechanical function and Ca2+ exchange in rabbit myocardium

1979 ◽  
Vol 236 (4) ◽  
pp. H525-H533 ◽  
Author(s):  
P. A. Poole-Wilson ◽  
G. A. Langer
Keyword(s):  
Cell Membrane ◽  
Myocardial Function ◽  
Interventricular Septum ◽  
Mechanical Function ◽  
Calcium Efflux ◽  
Stimulation Rate ◽  
Extracellular Acidosis ◽  
Rapid Fall ◽  
Rabbit Myocardium ◽  
Calcium Exchange

The effects of acidosis on myocardial function and calcium exchange have been studied in the isolated but arterially perfused interventricular septum of the rabbit. Temperature was 28 degrees C and stimulation rate 48 beats/min. Acidosis was induced either by increase of the perfusate PCO2 (pH reduced from 7.35 to 6.68) or by decrease of the bicarbonate-chloride ratio (pH 7.35 to 6.72). The effect on calcium efflux was assessed by introduction of acidosis at different times during the washout of 45Ca2+ from the muscle. The uptake of 47Ca2+ was recorded directly with a NaI crystal and counter. An increase of perfusate PCO2 caused a rapid fall in developed tension. The efflux of slowly exchanging 45Ca2+ and the uptake of 47Ca2+ were inhibited. There was no rapid displacement of calcium from the muscle. Decrease of the bicarbonate-chloride ratio caused a slower fall of developed tension and neither the efflux nor uptake of calcium were altered. These results suggest that developed tension and calcium exchange in the myocardium are more responsive to acidosis within the cell or cell membrane than to extracellular acidosis.

Acute effects of quinidine on K exchange and distribution in the dog ventricle

1960 ◽  
Vol 199 (1) ◽  
pp. 151-156 ◽  
Author(s):  
Hadley L. Conn ◽  
John C. Wood
Keyword(s):  
Oxygen Consumption ◽  
Gas Exchange ◽  
Action Potential ◽  
Respiratory Quotient ◽  
Resting Potential ◽  
Acute Effects ◽  
Dog Heart ◽  
Potassium Influx ◽  
Potassium Exchange ◽  
Potassium Metabolism

Some of the effects of quinidine on potassium metabolism and gas exchange were studied in the isolated perfused dog heart. The major changes found were an increase in cell K and transcellular K exchange, and a decrease in oxygen consumption and respiratory quotient. The increase in K exchange was apparently due to an increased resting potential potassium exchange with little or no alteration in exchange during the action potential. The accumulation of cell K seemed to be dependent mainly on an initial resting phase increase in potassium influx.

Effect of Ouabain in Therapeutic Concentrations on K+ Exchange and Contraction of Human and Rabbit Myocardium

1979 ◽  
Vol 57 (5) ◽  
pp. 415-420 ◽  
Author(s):  
P. A. Poole-Wilson ◽  
E. Galindez ◽  
C. H. Fry
Keyword(s):  
Positive Inotropic Effect ◽  
Sodium Pump ◽  
Interventricular Septum ◽  
Human Myocardium ◽  
Papillary Muscles ◽  
Ventricular Muscle ◽  
No Net Loss ◽  
Rabbit Myocardium

1. Experiments were undertaken on strips of human atrial and ventricular muscle, on right ventricular rabbit papillary muscles and on the rabbit interventricular septum. 2. In all preparations an increase of developed tension after 30 min exposure to ouabain was apparent only at or above a concentration of 10−7 mol/l (73 μg/l). 3. In the rabbit septum there was a net loss of potassium on exposure to ouabain if the concentration was greater than 10−7 mol/l. There was no net loss, or gain, of potassium at lower concentrations. Loss of potassium, indicating inhibition of the sodium pump, could not be dissociated from the positive inotropic effect of ouabain. 4. The greater sensitivity to ouabain of human myocardium in vivo (10−8 mol/l) than in vitro (10−7 mol/l) may be due to cellular changes occurring in isolated preparations.

Outward current and repolarization in hypoxic rat myocardium

1983 ◽  
Vol 244 (3) ◽  
pp. H341-H350
Author(s):  
C. H. Conrad ◽  
R. G. Mark ◽  
O. H. Bing
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Outward Current ◽  
Iodoacetic Acid ◽  
Mechanical Activity ◽  
Potential Range ◽  
Papillary Muscles ◽  
Rat Myocardium ◽  
Cable Properties ◽  
Sucrose Gap

We studied the effects of brief periods (20-30 min) of hypoxia in the presence of 5 and 50 mM glucose and of glycolytic blockade (10(-4) M iodoacetic acid, IAA) on action potentials, membrane currents, and mechanical activity in rat ventricular papillary muscles using a single sucrose gap voltage-clamp technique. Steady-state outward current (iss) was determined at the end of a 500-ms clamp to the test potential following a 600-ms clamp to a holding potential of -50 mV. In the presence of 5 mM glucose, hypoxia resulted in a decrease in action potential duration (APD) and an increase in iss (on the order of 60% at 0 mV) over the potential range studied. The increase in iss did not appear to be due to an increase in leakage current or to a change in the cable properties of the preparation. Addition of 50 mM glucose prevented the change in both APD and iss with hypoxia. In addition, glycolytic blockade with IAA did not alter iss in the presence of oxygen. We conclude that an increase in iss appears to be a major factor in the abbreviation of rat ventricular action potential seen with hypoxia. Glycolysis appears to be a sufficient (with 50 mM glucose) but not necessary source of energy for the maintenance of normal iss.

Inter-Basal and Septal Connections of Papillary Muscles - An Anatomical Rationale for Rhythmic Opening of AV Valves - A Multicentric Medical College Based Cross Sectional Study

2021 ◽  
Vol 8 (31) ◽  
pp. 2865-2869
Author(s):  
Praveen Mulki Shenoy ◽  
Amith Ramos ◽  
Narasimha Pai ◽  
Bharath Shetty ◽  
Aravind Pallipady Rao
Keyword(s):  
Left Ventricle ◽  
Papillary Muscle ◽  
Interventricular Septum ◽  
Cross Sectional Study ◽  
Papillary Muscles ◽  
Cross Sectional ◽  
Medical College ◽  
Moderator Band ◽  
Almost All ◽  
And Function

BACKGROUND The papillary muscle basal connections have significant clinical implications. Variety of studies done on its morphology and function by various specialists in different departments. A close look on these revealed the interconnections of papillary muscles to one another and to the interventricular septum of both ventricles is related to uncoordinated contractions of papillary muscles, leading to hyper or hypokinesia or prolapse or even its rupture. METHODS Our study done in 25 formalin soaked hearts revealed after the deep and meticulous dissection, reflecting the walls of ventricles laterally the numerous interconnections of papillary muscles at its bases and IVS. Ventricles are opened by inverted ‘L’ shaped incision and its reflected more laterally till all the papillary muscles is visible in one frame after incising the moderator band. The connections were noted, measured, photographed, tabulated, compared with similar studies and analysed with experts with respective fields. RESULTS Almost all the specimens did have the interconnections. Further the post mortem findings of the cardiac related deaths with involvement of papillary muscles suggest damage to such ‘bridges’. The moderator band extensions to the base of right APM, and its extension to the posterior groups is noted in all the specimens. The bridge from the IVS to bases of both the groups of papillary muscles is noted in left ventricle. In90% of specimens the one PPM is found to be loosely connected, more so in left ventricle. CONCLUSIONS We are of a conclusion that such basal interconnections and to the interventricular septum are responsible for rhythmic contractions of papillary muscles of both ventricles. Since the AV valves have to open simultaneously, interconnections becomes mandatory as the impulse has to reach it before it reaches the trabeculae carniae. One of the Posterior papillary muscles is loosely connected to other papillary muscles, may be the reason for its rupture, more so in left ventricle. KEYWORDS Papillary Muscle, Interbasal Connection, Moderator Band, Valvular Prolapse, AV Valves

Effects of octanol on canine subendocardial Purkinje-to-ventricular transmission

1985 ◽  
Vol 249 (6) ◽  
pp. H1228-H1231 ◽  
Author(s):  
R. W. Joyner ◽  
E. D. Overholt
Keyword(s):  
Action Potential ◽  
Conduction Velocity ◽  
Current Flow ◽  
Conduction Delay ◽  
Papillary Muscles ◽  
Maximal Rate ◽  
Gap Junctional ◽  
Junctional Resistance ◽  
P Cells

The effects of 0.2 mM octanol on action potential propagation were investigated using in vitro preparations of canine papillary muscles. In these preparations an action potential initiated in the superficial Purkinje (P) layer propagates across specific Purkinje-ventricular junction (PVJ) sites into the underlying ventricular (V) layer. The conduction delay at PVJ sites increased from 4.85 +/- 1.55 to 8.85 +/- 3.34 (mean +/- SD) ms (n = 10, P less than 0.005), an 82% increase. However, propagation within the V syncytium was much less affected, with a decrease of conduction velocity by only 10% and a decrease in the maximal rate of rise of the action potential of 23%. The results indicate that octanol, which has previously been shown to increase gap junctional resistance, has a preferential effect on PVJ sites, as predicted by the hypothesis that there is a restricted pathway for intracellular current flow from P cells to V cells at these sites.

Time course of postnatal changes in rat heart action potential and in transient outward current is different

1994 ◽  
Vol 267 (3) ◽  
pp. H1157-H1166 ◽  
Author(s):  
G. M. Wahler ◽  
S. J. Dollinger ◽  
J. M. Smith ◽  
K. L. Flemal
Keyword(s):  
Action Potential ◽  
Rat Heart ◽  
Action Potentials ◽  
Time Course ◽  
Outward Current ◽  
Transient Outward Current ◽  
Papillary Muscles ◽  
Isolated Cells ◽  
Time Courses ◽  
Action Potential Shortening

The rat ventricular action potential shortens after birth. The contribution of increases in the transient outward current (Ito) to postnatal action potential shortening was assessed by measuring Ito in isolated cells and by determining the effect of 2 mM 4-aminopyridine (4-AP) on the action potentials of papillary muscles. 4-AP had no effect on 1-day action potential duration at 25% repolarization (APD25), and 1-day cells had little Ito. In 8- to 10-day muscles, 4-AP caused a small, but significant, increase in APD25. Ito increased slightly between day 1 and days 8-10, but this increase was not significant. Most of the increase in Ito (79%) and in the response to 4-AP (64%) occurred between days 8-10 and adult; however, approximately 75% of the APD25 shortening took place by days 8-10. Thus, while Ito may contribute to repolarization in late neonatal and adult cells, the different time courses of action potential shortening and increases in Ito suggest that changes in Ito are unlikely to be responsible for most of the postnatal action potential shortening.

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