Characteristics of the K-252a-induced increase in calcium uptake in PC12 cells.

K-252a treatment produced a 30-50% increase in the uptake of radioactive calcium by PC12 cells within 3-4 minutes. The increase in uptake was partially blocked by inhibitors of voltage-operated calcium channels, such as nifedipine, but not by inhibitors of receptor-operated calcium channels, such as nickel or suramin. Introduction of phosphatase 2A into the cells completely blocked the effect of K-252a.

Signal transduction and Ca2+ uptake activated by endothelins in rat brain endothelial cells.

The activation of signal transduction pathways by endothelin-1 or endothelin-3 were investigated in rat cerebromicrovascular endothelial cells. Endothelin-1 induced a rapid increase in inositol triphosphate (IP3) formation in these cells, whereas endothelin-3 was only moderately effective at high concentrations. Both endothelins also increased uptake of 45Ca2+ in these cells.

Effects of ATP and UTP in pheochromocytoma PC12 cells: evidence for the presence of three P2 receptors, only one of which subserves stimulation of norepinephrine release.

1. In pheochromocytoma PC12 cells ATP and, to a lesser extent, 2-methylthioATP stimulate phosphoinositide breakdown, release of intracellular calcium, and influx of external calcium, leading to stimulation of norepinephrine release. In contrast, although UTP also stimulates phosphoinositide breakdown, release of intracellular calcium, and influx of external calcium, there is no stimulation of norepinephrine release.

The long-term down-regulation of dihydropyridine receptors by Bay K 8644 in PC12 cells.

Treatment of PC12 cells with Bay K 8644 for 12 hr or more leads to an almost 80% decrease in the subsequent ability of Bay K 8644 to stimulate the uptake of radioactive calcium into the cells. This effect is a property of the S(-)isomer of Bay K 8644; pre-treatment with the R(+)isomer, now known to be a calcium channel blocker, has the opposite effect. This treatment is specific in that it does not interfere with the stimulation of calcium uptake by potassium, ATP, or nerve growth factor.

Pardaxin-stimulated calcium uptake in PC12 cells is blocked by cadmium and is not mediated by L-type calcium channels.

Pardaxin is an excitatory neurotoxin which triggers neurotransmitter release as a result of voltage-dependent pore formation within the neuronal membrane. We have used several pharmacological manipulations of calcium influx to characterize pardaxin pore activity in PC12 cells in culture. Pardaxin stimulates the uptake of radioactive calcium into PC12 cells in a dose dependent fashion (ED50 of 0.