The free intracellular Ca2+ concentration ([Ca2+]i) is governed by the balance between the activation of Ca2+ channels and buffering and efflux processes. We tested the hypothesis that Ca2+ efflux pathways are susceptible to modulation. The whole-cell patch-clamp technique was used in combination with Indo-1-based microfluorometry to record Ca2+ current and [Ca2+]i simultaneously from single ra...

A method for clamping cytosolic free Ca2+ ([Ca2+]i) in cultures of rat sympathetic neurons at or below resting levels for several days was devised to determine whether Ca2+ signals are required for neurite outgrowth from neurons that depend on Nerve Growth Factor (NGF) for their growth and survival. To control [Ca2+]i, normal Ca2+ influx was eliminated by titration of extracellular Ca2+ with EG...

The synergistic action of cytosolic Ca2+ and inositol 1,4,5-trisphosphate (InsP3) in releasing intracellular Ca2+ stores has been suggested to be responsible for the complex intracellular Ca2 signals observed during hormonal stimulation of many cell types. However, the ability of cytosolic Ca2+ to potentiate Ca2+ release has recently been questioned because of the observed inhibitory effects of...

Following receptor activation in Xenopus oocytes, spiral waves of intracellular Ca2+ release were observed. We have identified key molecular elements in the pathway that give rise to Ca2+ excitability. The patterns of Ca2+ release produced by GTP-gamma-S and by inositol 1,4,5-trisphosphate (IP3) are indistinguishable from receptor-induced Ca2+ patterns. The regenerative Ca2+ activity is critica...

The tight control of blood Ca2+ levels within a narrow range is essential for the performance of vital physiologic functions. Muscle contraction, neuronal excitation, and intracellular signaling processes acquisitively require Ca2+. It is the concerted action of intestine, bone, and kidney that controls the Ca2+ balance through the regulation of intestinal absorption, bone (de)mineralization, a...

We assessed the pathways by which excitatory and inhibitory neurotransmitters elicit postsynaptic changes in [Ca2+]i in brain slices of developing rat and cat neocortex, using fura 2. Glutamate, NMDA, and quisqualate transiently elevated [Ca2%]i in all neurons. While the quisqualate response relied exclusively on voltage-gated Ca2+ channels, almost all of the NMDA-induced Ca2+ influx was via th...

Hepatocytes are well coupled by gap junctions, which allow the diffusion of small molecules between cells. Although gap junctions in many tissues are permeable to molecules larger than cAMP and in several preparations gap junctions pass cAMP itself, little direct evidence supports permeation by other second-messenger species. Ca2+, perhaps the smallest second messenger, would be expected to cro...

The myoplasmic free Ca2+concentration ([Ca2+]i) was measured in intact single fibers from mouse skeletal muscle with the fluorescent Ca2+ indicator indo 1. Some fibers were perfused in a solution in which the concentration of Na+ was reduced from 145.4 to 0.4 mM (low-Na+solution) in an attempt to activate reverse-mode Na+/Ca2+exchange (Ca2+ entry in exchange for Na+ leaving the cell). Under nor...

In A7r5 smooth muscle cells, vasopressin stimulates release of Ca2+ from intracellular stores and Ca2+ entry, and it inhibits adenylyl cyclase (AC) activity. Inhibition of AC is prevented by inhibition of phospholipase C or when the increase in cytosolic [Ca2+] is prevented by the Ca2+ buffer, BAPTA. It is unaffected by pertussis toxin, inhibition of protein kinase C, or L-type Ca2+ channels or...

Transforming growth factor-beta (TGF-beta) has been implicated as a key factor in mediating many cellular processes germane to disease pathogenesis, including diabetic vascular complications. TGF-beta alters cytosolic [Ca2+] ([Ca2+]c) signals, which in some cases may result from the downregulation of the IP3 receptor Ca2+ channels (IP3R). Ca2+ released by IP3Rs is effectively transferred from e...