Reduction of the transsarcolemmal [Na] gradient in rabbit cardiac muscle leads to an increase in the force of contraction. This has frequently been attributed to alteration of Ca movements via the sarcolemmal Na/Ca exchange system. However, the specific mechanisms that mediate the increased force at individual contractions have not been clearly established. In the present study, the [Na] gradie...

The effects of Na-free Li solution on the electrical and mechanical activities were examined in a bullfrog's ventricular strip. The action potential showed a triphasic change during Na-free perfusion: the initial decrease in the overshoot and duration, the secondary restoration and the gradual decrease in the membrane potential. The twitch contraction also changed in a triphasic manner: the ini...

It is well established that spasm of an arterial and venous graft conduit may occur during harvesting or after coronary artery bypass grafting (CABG). The antivasoconstrictor effect of levcromakalim and rilmakalim, K(+) channel openers (KCOs), was studied in isolated human internal mammary artery (HIMA) and human saphenous vein (HSV) prepared for CABG. HIMA and HSV rings were contracted by elec...

21 Prolongation of the Ca transient and action potential (AP) durations are two characteristic changes in myocyte physiology in the 21 1 21 21 failing human heart. The hypothesis of this study is that Ca influx via reverse mode Na /Ca exchanger (NCX) or via L-type Ca 21 channels directly activates contraction in failing human myocytes while in normal myocytes this Ca is transported into the sar...

Shear stress and tyrosine phosphatase inhibitors have been shown to activate the endothelial NO synthase (eNOS) in a Ca2+/calmodulin-independent manner. We report here that isometric contraction of rabbit aorta activates eNOS by a pharmacologically identical pathway. Endothelium-intact aortic rings were precontracted under isometric conditions up to 60% of the maximal phenylephrine-induced tone...

The sympathetic nervous system and its neurotransmitter effectors are undeniably important to blood pressure control. We made the novel discovery that perivascular adipose tissue (PVAT) contains significant concentrations of catecholamines. We hypothesized that PVAT contains sufficient releasable catecholamines to affect vascular function. HPLC, isometric contractility, immunohistochemistry, wh...

We examined the effects of intracellular acidosis produced by washout of NH4Cl on [Ca2+]i transients (indo-1 fluorescence), cell contraction (video motion detector), and 45Ca and 24Na fluxes in cultured chick embryo ventricular myocytes. Exposure of cells to 10 mM NH4Cl produced intracellular alkalosis (pH 7.6), and subsequent washout resulted in a transient acidosis (pH 6.5). Exposure to 10 mM...

Inhibitory effects of cernitin pollen extract (CN-009), consisting of T-60 (a water-soluble extract) and GBX (an acetone-soluble extract) at a ratio of 20:1, were investigated in rat urethral smooth muscle and diaphragm. In the urethral smooth muscle, CN-009 (3.0 x 10(-4) approximately 3.0 x 10(-3) g/ml), T-60 and GBX (corresponding to CN-009) concentration-dependently inhibited the noradrenali...

Stimulation of the tracheal muscle bundle by acetylcholine (ACh) results in the generation of asynchronous repetitive Ca2+ waves (ACW) in intact tracheal smooth muscle (TSM) cells. We showed previously that ACW underlie cholinergic excitation-contraction coupling in porcine TSM and that Ca2+ entry through the L-type voltage-gated Ca2+ channel (VGCC) contributes partially to maintenance of the A...

UNLABELLED Prolongation of the Ca2+ transient and action potential (AP) durations are two characteristic changes in myocyte physiology in the failing human heart. The hypothesis of this study is that Ca2+ influx via reverse mode Na+/Ca2+ exchanger (NCX) or via L-type Ca2+ channels directly activates contraction in failing human myocytes while in normal myocytes this Ca2+ is transported into the...