RATIONALE The development of a refractory period for Ca2+ spark initiation after Ca2+ release in cardiac myocytes should inhibit further Ca2+ release during the action potential plateau. However, Ca2+ release sites that did not initially activate or which have prematurely recovered from refractoriness might release Ca2+ later during the action potential and alter the cell-wide Ca2+ transient. ...

Ca2+ concentration in peroxisomal matrix ([Ca2+](perox)) has been monitored dynamically in mammalian cells expressing variants of Ca2+-sensitive aequorin specifically targeted to peroxisomes. Upon stimulation with agonists that induce Ca2+ release from intracellular stores, peroxisomes transiently take up Ca2+ reaching peak values in the lumen as high as 50-100 microm, depending on cell types. ...

1. Electrophysiological measurements of Ca2+ influx using patch clamp methodology were combined with fluorescent monitoring of the free intracellular calcium concentration ([Ca2+]i) to determine mechanisms of Ca2+ regulation in isolated nerve endings from the rat neurohypophysis. 2. Application of step depolarizations under voltage clamp resulted in voltage-dependent calcium influx (ICa) and in...

Dennettia tripetala (DT) is a tree found in rain forest belt of Nigeria, Cameroon and Ivory Coast. The seed commonly used preparing food for mothers after delivery because it believed to play role postpartum uterine contraction. There however no scientific evidence validating this claim. Hence, the study aimed investigate effects DT on non-pregnant pregnant uterus using mouse model. dried seeds...

The mechanism underlying the generation of cytosolic free Ca2+ ([Ca2+]i) oscillations by bombesin, a receptor agonist activating phospholipase C, in insulin secreting HIT-T15 cells was investigated. At 25 microM, 61% of cells displayed [Ca2+]i oscillations with variable patterns. The bombesin-induced [Ca2+]i oscillations could last more than 1 h and glucose was required for maintaining these [C...

Transcellular Ca2+ transport in the distal nephron involves passive Ca2+ influx at the apical membrane, diffusion through the cytosol and active extrusion across the opposing basolateral membrane. The molecular identity of the apical Ca2+ entry step is still elusive, but its regulatory aspects have been analyzed in the present study. To this end, rabbit connecting and cortical collecting tubula...

Adenophostin-A, a novel compound isolated from cultures of Penicillium brevicompactum, has been shown to stimulate Ca2+ release from inositol-1,4,5-trisphosphate (IP3)-sensitive Ca2+ stores in microsomal preparations, permeabilized cells, and lipid vesicles containing purified IP3 receptor. The purpose of the current study was to compare the effects of adenophostin-A and IP3 on Ca2+ release fro...

A rise in cytosolic Ca2+ concentration ([Ca2+]cyt) in pulmonary artery smooth muscle cells (PASMC) is an important stimulus for cell contraction, migration, and proliferation. Depletion of intracellular Ca2+ stores opens store-operated Ca2+ channels (SOC) and causes Ca2+ entry. Transient receptor potential (TRP) cation channels that are permeable to Na+ and Ca2+ are believed to form functional ...

Endoplasmic reticulum (ER) Ca2+ refilling is an active process to ensure an appropriate ER Ca2+ content under basal conditions and to maintain or restore ER Ca2+ concentration during/after cell stimulation. The mechanisms to achieve successful ER Ca2+ refilling are multiple and built on a concerted action of processes that provide a suitable reservoir for Ca2+ sequestration into the ER. Despite...

The concerted action of inositol 1,4,5-trisphosphate (IP3) and Ca2+ on the IP3 receptor Ca2+ release channel (IP3R) is a fundamental step in the generation of cytosolic Ca2+ oscillations and waves, which underlie Ca2+ signaling in many cells. Mitochondria appear in close association with regions of endoplasmic reticulum (ER) enriched in IP3R and are particularly responsive to IP3-induced increa...