Quinidine and its stereoisomer quinine suppress various membrane conductances in a variety of cells Recently quinidine has been classified as a putative blocker of the Na-Ca exchange in heart muscle (Mentrard et al. 1984; Chapman et al. 1984). The effects of quinidine on the contractile responses of the ureter muscle of the guinea-pig associated with both the entry of Ca via voltage-operated Ca...

The significance of altered Ca2+ influx and efflux pathways on contractile abnormalities of myocytes isolated from rat hearts 3 wk after myocardial infarction (MI) was investigated by varying extracellular Ca2+ concentration ([Ca2+]o, 0.6-5.0 mM) and pacing frequency (0.1-5.0 Hz). Myocytes isolated from 3-wk MI hearts were significantly longer than those from sham-treated (Sham) hearts (125 +/-...

Chronic intermittent hypobaric hypoxia (CIHH) has been shown to attenuate intracellular Na(+) accumulation and Ca(2+) overload during ischemia and reperfusion (I/R), both of which are closely related to the outcome of myocardial damage. Na/K pump plays an essential role in maintaining the equilibrium of intracellular Na(+) and Ca(2+) during I/R. It has been shown that enhancement of Na/K pump a...

PURPOSE To test whether changes in extracellular pH (pHe) in an in vitro preparation of the cat ophthalmociliary artery affect passive tone and agonist responses and whether the endothelial cells are mediators of any pH-induced effect. This will determine the ability of the ophthalmociliary artery to influence retinal and choroidal blood flow in response to metabolic stimuli. METHODS The isom...

The role of membrane depolarization in the histamine-induced contraction of the rabbit middle cerebral artery was examined by simultaneous measurements of membrane potential and isometric force. Histamine (1-100 microM) induced a concentration-dependent sustained contraction associated with sustained depolarization. Action potentials were observed during depolarization caused by histamine but n...

Ion channel function is fundamental to the existence of life. In metazoans, the coordinate activities of voltage-gated Na(+) channels underlie cellular excitability and control neuronal communication, cardiac excitation-contraction coupling, and skeletal muscle function. However, despite decades of research and linkage of Na(+) channel dysfunction with arrhythmia, epilepsy, and myotonia, little...

In our previous report, we showed that L-arginine induced depolarization of smoolh muscle cells of the rat portal vein with an increasecl contraction. To clarify the ionic mechanism of the membrane depolarization, the effect of I.-arginine on the holding current was studied in freshly isolated smooth muscle cells of the rat portal vein. The whole-cell patch-clamp teehnique was used, with the me...

The aim of this investigation was to evaluate serotonin (5-HT) action on isolated human umbilical arteries (HUA) from normal and gestational diabetes mellitus (GDM) pregnancies. 5-HT caused HUA contraction in a concentration-dependent manner in both investigated groups but with lower efficacy in GDM. After endothelial denudation or in the presence of indomethacin (cyclooxygenase inhibitor), the...

The effects of an extracellular sodium (Na) concentration of 200 mM on function, ionic exchange, and water movements were examined in the vascularly perfused rabbit intraventricular septum. When the perfusate was switched from 142 mMNa to 200 mMNa, dP/ dt fell 20.4% over 2 minutes; dP/dt then recovered to the control level. The time course of the functional recovery correlated with the uptake o...