Introduction: we have recently reported the presence of two potassium currents with 598 and 368 pS conductance in the rough endoplasmic reticulum (RER) membrane. The 598 pS channel was voltage dependent and ATP sensitive. However, the 368 pS channel was rarely observed and its identity remained obscure. Since cationic channels in intracellular organelles such as mitochondria and RER play imp...

The effect of the plant alkaloid ryanodine on the skeletal muscle sarcoplasmic reticulum Ca2+ release channel was studied by determining the Ca2+ permeability of "heavy" vesicles passively loaded with 45Ca2+ in the presence or absence of ryanodine. Depending on the experimental conditions, ryanodine either stimulated or inhibited Ca2+ efflux. Vesicles were rendered permeable to 45Ca2+ at a ryan...

Voltage-gated Na and Ca2+ channels comprise distinct ion channel superfamilies, yet the carboxy tails of these channels exhibit high homology, hinting at a long-shared and purposeful module. For different Ca2+ channels, carboxyl-tail interactions with calmodulin do elaborate robust and similar forms of Ca2+ regulation. However, Na channels have only shown subtler Ca2+ modulation that differs am...

In endothelial cells, stretch-activated cation channels have been proposed to act as mechanosensors for changes in hemodynamic forces. We have identified a novel mechanosensitive pressure-activated channel in intact endothelium from rat aorta and mesenteric artery. The 18-pS cation channel responded with a multifold increase in channel activity when positive pressure was applied to the luminal ...

A computer model is developed for the characterization of Ca2+-induced calcium release (CICR) from the sarcoplasmic reticulum (SR) in the rat ventricular cell. The fluid compartment model is configured to describe the trigger Ca2+ influx (ICa,L) through the membrane of the sarcolemma (SL); the diffusion of Ca2+ throughout a small cleft space, which is located between the SL and the junctional s...

Undifferentiated monolayers of the hamster vas deferens smooth-muscle cell line, DDT1MF-2, were grown on glass coverslips and loaded with the Ca(2+)-sensitive fluorescent dye fura-2. Stimulation with histamine produced a rapid and maintained increase in intracellular free Ca2+ ([Ca2+]i), with an EC50 of 7.0 +/- 0.7 microM. The initial rise in [Ca2+]i can be attributed to Ca2+ release from intra...

Voltage-dependent L-type Ca2+ channels select for Ca2+ and other divalent cations by high-affinity Ca2+ binding and ion-ion interactions in the permeation pathway. We have recently identified a series of highly conserved glutamate residues, located within the SS2 segments of each of the four repeats of the human heart Ca2+ channel alpha 1 subunit, as major determinants of ion selectivity of the...

The influx of Ca2+ and its subsequent intracellular increase are required for the acrosome reaction of sea urchin sperm to occur. Spermatozoa must undergo this reaction, which is triggered by the egg jelly, in order to fertilize the egg. Here, the egg jelly-induced Ca2+ influx mechanisms have been studied in sperm loaded with FURA-2 using Mn2+ under the assumption that this divalent ion is an i...

Cilnidipine is a unique dihydropyridine derivative Ca2+ channel blocker with an inhibitory action on the sympathetic N-type Ca2+ channels (Uneyama et al., 1999a). It has been clarified that cilnidipine exerts antisympathetic actions in various examinations from cell to human levels. Furthermore, its renoprotective, neuroprotective and cardioprotective effects have been demonstrated in clinical ...