Extracellular calcium transients were resolved within the time course of single contraction cycles in rabbit left atrium using tetramethylmurexide (2 mM) as the calcium-sensitive dye (150-250 microM total calcium, 80-150 microM free calcium). Net extracellular calcium depletion began within 2-4 ms upon excitation; over the following 5-20 ms, depletion continued steeply and amounted to 0.2 mumol...

The DNA-synthetic and proliferative activities of freshly isolated, nontumorigenic C3H mouse skin cells (first passage) were lowest when the extracellular free (or ionic) calcium level was reduced to between 0.05 and 0.1 mM, whereas the extracellular free calcium level in cultures of repeatedly passaged, preneoplastic C3H/10T1/2 and MCA-C3H/10T1/2 type I mouse fetal fibroblasts had to be reduce...

Activation of the NLRP3 inflammasome enables monocytes and macrophages to release high levels of interleukin-1β during inflammatory responses. Concentrations of extracellular calcium can increase at sites of infection, inflammation or cell activation. Here we show that increased extracellular calcium activates the NLRP3 inflammasome via stimulation of G protein-coupled calcium sensing receptors...

Removal of extracellular calcium may result in depolarization of the resting cell membrane potential. This has been attributed to the stabilizing action of calcium on the ionic permeability of the cell membrane. It is unknown whether this phenomenon is exclusively mediated by extracellular calcium or through associated changes in intracellular calcium. To examine this, we exposed rat aortic smo...

Alterations in parathyroid glandular sensitivity to calcium may contribute to the hypersecretion of PTH in hyperparathyroidism. Since the cytosolic calcium concentration may mediate the effects of extracellular calcium on PTH release, we have employed the calcium-sensitive intracellular dye QUIN-2 to examine the relationship between extracellular calcium, cytosolic calcium, and PTH secretion in...

We have used a spectrophotometric method to monitor mean free extracellular calcium concentrations in isolated left atria of guinea pigs via extracellular application of the calcium-sensitive absorption dyes, antipyrylazo III and tetramethylmurexide. Exchange of extracellular free calcium with the bathing medium takes several minutes and closely parallels contractile response in this preparatio...

It has been proposed that extracellular cGMP modulates the ability to learn a Y maze task, but the underlying mechanisms remained unknown. Here we show that extracellular cGMP, at physiological concentrations, modulates learning in the Y maze in a biphasic way by modulating the glutamate-nitric oxide-cGMP pathway in cerebellum. Extracellular cGMP reduces glycine receptors activation inducing a ...

Extracellular calcium transients were monitored with 2 mM tetramethylmurexide at low calcium (250 microM total, 130 microM free), and action potentials were monitored together with developed tension at normal calcium (1.3 mM) during the production and decay of post-stimulatory potentiation in rabbit left atrial strips. At normal calcium, the contractile potentiation produced by a brief burst of...

Both intra- and extracellular calcium play multiple roles in the physiology and pathophysiology of cardiomyocytes, especially in stimulus-contraction coupling. The intracellular calcium level is closely controlled through the concerted actions of calcium channels, exchangers, and pumps; however, the expression and function(s) of the so-called calcium-sensing receptor (CaR) in the heart remain l...