Suction electrode in frog heart ventricle: DISCUSSION (part 4) / buy flovent inhaler

 On the other hand, when tetrodotoxin was present or sucrose was substituted for sodium ions in the tip of the suction electrode (elimination of sodium channels), MAP development was suppressed. This indicates that suction reversibly increases the probability of sodium channel opening. The influx of sodium into the cells might then cause potassium efflux into the extracellular space. Calcium fluxes are evidently not so important because inhibition of main calcium sources – sarcolemmal L-type calcium channel by verapamil and La3+ – influenced the time course of changes in MAP only slightly and did not influence MAP amplitude.AK changes correlated well with the changes in MP, with the Na+/K+-ATPase activity profile and with the density [ H]ouabain binding sites in the base, middle and apex of frog ventricular muscle. Suppression of the second phase of a0K after cooling of the tissue to 2°C or after addition of ouabain (10 to 4 mmol/L) demonstrated that the decrease in a0K is coupled directly with the transport Na+/K+-ATPase. The extent of the second phase also correlated well with the activity of this enzyme and with density of ouabain binding sites in different parts of the ventricle. The absence of the second phase of a0K in the absence of spontaneous contractions  also points to the importance of sodium entry during the development of MAP as a necessary prerequisite for Na+/K+-ATPase action and removal of excess potassium ions from the extracellular space. You can find best quality treatment now – buy flovent inhaler to see how cheap it is.

Osmotic swelling causes a greater increase in radial than in longitudinal dimensions and dilution of intracellular contents. Mechanical stretch (dilation) results in an increase in longitudinal dimensions and a decrease in radial dimensions. Suction applied on a cellular level to a patch pipette causes local deformation of a small patch of the membrane sucked up into the patch pipette, with the changes in tensions dependent on the geometry of the patch sucked to the pipette. On the other hand, hydraulic inflation (application of the agent via patch pipette), causes distension similar to osmotic swelling . Recent studies of this topic suggest a role for phosphorylation cascades in mechanical-biochemical transduction.

 

Category: Cardiology

Tags: Extracellular potassium activity, Frog ventricle myocardium, Membrane potential, Monophasic action potential, Na+/K+ -ATPase activity, Ultrastructure

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