Electrical field stimulation (EFS) produced a biphasic contractile response; viz. initial rapid phasic contraction and second slow tonic contraction, in isolated guinea pig vas deferens. Pretreatment with the substrate of nitric oxide (NO) synthase (NOS), 1 mM L-arginine (L-ARG), augmented both the initial rapid and the second slow contractile responses to EFS (5 Hz, 0.5 msec, 30 V, for 30 sec)...

BACKGROUND Carfilzomib (CFZ) is a new proteasome inhibitor used for the treatment of multiple myeloma. Besides heart failure, angina and myocardial ischemia occurred following administration of CFZ, which is not contraindicated in patients with recent myocardial infarction/unstable angina excluded from the safety trials. AIM OF STUDY To test the effects of CFZ (10-9 to 10-7mol/L) on vascular ...

Phospholemman (PLM) regulates contractility and Ca(2+) homeostasis in cardiac myocytes. We characterized excitation-contraction coupling in myocytes isolated from PLM-deficient mice backbred to a pure congenic C57BL/6 background. Cell length, cell width, and whole cell capacitance were not different between wild-type and PLM-null myocytes. Compared with wild-type myocytes, Western blots indicat...

The relative contribution of the sarcoplasmic reticulum (SR), the L-type Ca(2+) channel and the Na(+)/Ca(2+) exchanger (NCX) were assessed in turtle ventricular myocytes using epifluorescent microscopy and electrophysiology. Confocal microscopy images of turtle myocytes revealed spindle-shaped cells, which lacked T-tubules and had a large surface area-to-volume ratio. Myocytes loaded with the f...

Changes in stimulation rate alter the electrical and mechanical characteristics of myocardial cells. We have investigated the possibility that intracellular sodium activity (aiNa) changes with stimulation and correlates with changes in contraction strength. Two kinds of liquid membrane Na+-selective microelectrodes were used to measure aiNa in guinea pig and sheep ventricular muscle and in shee...

Excitation-contraction coupling was characterized in scorpion striated muscle fibers using standard microelectrode techniques as employed in studies on vertebrate skeletal muscle. The action potential of scorpion muscle consists of two phases of regenerative activity. A relatively fast, overshooting initial spike is followed by a prolonged after-discharge of smaller, repetitive spikes. This aft...

BACKGROUND In the failing human heart, altered Ca2+ homeostasis causes contractile dysfunction. Because Ca2+ and Na+ homeostasis are intimately linked through the Na+/Ca2+ exchanger, we compared the regulation of [Na+]i in nonfailing (NF) and failing human myocardium. METHODS AND RESULTS [Na+]i was measured in SBFI-loaded muscle strips. At slow pacing rates (0.25 Hz, 37 degrees C), isometric ...

Hyvelin, Jean-Marc, Clare O’Connor, and Paul McLoughlin. Effect of changes in pH on wall tension in isolated rat pulmonary artery: role of the RhoA/Rho-kinase pathway. Am J Physiol Lung Cell Mol Physiol 287: L673–L684, 2004. First published February 6, 2004; 10.1152/ajplung.00331.2003.—Pulmonary arteries (PA) are resistant to the vasodilator effects of extracellular acidosis in systemic vessels...

OBJECTIVE The T-tubule membrane network is integrally involved in excitation-contraction coupling in ventricular myocytes. Ventricular myocytes from canine hearts with tachycardia-induced dilated cardiomyopathy exhibit a decrease in accessible T-tubules to the membrane-impermeant dye, di8-ANNEPs. The present study investigated the mechanism of loss of T-tubule staining and examined for changes ...