Smaller Ca2+ transients and systolic dysfunction in heart failure (HF) can be largely explained by reduced total sarcoplasmic reticulum (SR) Ca2+ content ([Ca]SRT). However, it is unknown whether low [Ca]SRT is manifest as reduced: (1) intra-SR free [Ca2+] ([Ca2+]SR), (2) intra-SR Ca2+ buffering, or (3) SR volume (as percentage of cell volume). Here we assess these possibilities in a well-chara...

To determine the effects of insulin on intracellular calcium and platelet aggregatory responses in hypertensive subjects with insulin resistance, we measured insulin sensitivity in terms of glucose disposal rate (GDR) by the hyperinsulinemic euglycemic clamp technique (GC) in 14 non-diabetic untreated hypertensive subjects, and determined basal ([Ca2+];) and thrombin-stimulated (T-[Ca2+];) plat...

BACKGROUND There is growing evidence suggesting involvement of L-type voltage-gated Ca2+ channels (VGCCs) in purinergic signaling mechanisms. However, detailed interplay between VGCCs and P2X receptors in intracellular Ca2+ mobilization is not well understood. This study examined relative contribution of the Ca2+ entry mechanisms and induced by this entry Ca2+ release from the intracellular sto...

The sarcolemmal Na(+)-Ca2+ exchanger is regulated by intracellular Ca2+ at a high affinity Ca2+ binding site separate from the Ca2+ transport site. Previous data have suggested that the Ca2+ regulatory site is located on the large intracellular loop of the Na(+)-Ca2+ exchange protein, and we have identified a high-affinity 45Ca2+ binding domain on this loop (Levitsky, D. O., D. A. Nicoll, and K...

Over the past two decades, a significant contribution to the pathophysiology of heart failure (HF) has been attributed to alterations of Ca2+ handling, which has been observed in myocytes isolated from failing hearts. Initially, a reduced Ca2+ transient amplitude due to a reduced Ca2+ reuptake rate by SERCA and enhanced extrusion of Ca2+ to the extracellular space by the Na+/Ca2+ exchanger had ...

Testosterone deficiency is associated with poor prognosis among patients chronic heart failure (HF). Physiological testosterone improves the exercise capacity of HF. In this study, we evaluated whether treatment physiological contributes to anti-fibrogenesis by modifying calcium homeostasis in cardiac fibroblasts and studied underlying mechanisms. Nitric oxide (NO) analyses, (Ca2+) fluorescence...

Gustatory transduction mechanisms for sucrose and amino acid sweeteners in gerbil taste cells were studied with Ca2+ imaging and whole cell recording techniques. A 100 mM sucrose stimulus with Ca2+ increased the intracellular Ca2+ concentration ([Ca2+]i) in sweet-sensitive taste cells of the taste bud, but the sucrose stimulus without Ca2+ did not change the [Ca2+]i. A 10 mM D-phenylalanine swe...

Unstimulated platelets maintain a low cytosolic free Ca2+ concentration and a steep plasma membrane Ca2+ gradient. The mechanisms that are required have not been completely defined. In the present studies, 45Ca2+ was used to examine the kinetics of Ca2+ exchange in intact unstimulated platelets. Quin2 was used to measure the cytosolic free Ca2+ concentration. Under steady-state conditions, the ...

The intracellular Ca2+ indicator, fura-2, was used to monitor changes in cytosolic [Ca2+] in parotid acinar cells. When parotid cells were incubated in a medium containing low [Ca2+], and [Ca2+] was restored to the physiological range, there was a small increase in cytosolic [Ca2+]. If, however, the cells were first activated by a muscarinic agonist, and receptor activation was terminated befor...

Intracellular Ca2+ store depletion induces Ca2+ entry across the plasma membrane, allowing the store to recharge. In our experiments, Ca2+ stores in pancreatic acinar cells were depleted by acetylcholine (ACh) stimulation in Ca2+-free solution. Thereafter, Ca2+ entry was only allowed through a CaCl2-containing pipette attached to the basal membrane. Recharging intracellular Ca2+ stores via a pa...