Store‐Operated Ca²⁺Influx and Voltage‐Gated Ca²⁺Channels Coupled to Exocytosis in Pheochromocytoma (PC12) Cells

Abstract

Microamperometry was used to monitor quantal catecholamine release from individual PC12 cells in response to raised extracellular K ϩ and caffeine. K ϩ -evoked exocytosis was entirely dependent on Ca 2ϩ influx through voltage-gated Ca 2ϩ channels, and of the subtypes of such channels present in these cells, influx through N-type was primarily responsible for triggering exocytosis. L-type channels played a minor role in mediating K ϩ -evoked secretion, whereas P/Q-type channels did not appear to be involved in secretion at all. Caffeine also evoked catecholamine release from PC12 cells, but only in the presence of extracellular Ca 2ϩ . Application of caffeine in Ca 2ϩ -free solutions evoked large, transient rises of [Ca 2ϩ ] i , but did not trigger exocytosis. When Ca 2ϩ was restored to the extracellular solution (in the absence of caffeine), store-operated Ca 2ϩ influx was observed, which evoked exocytosis. The amount of secretion evoked by this influx pathway was far greater than release triggered by influx through L-type Ca 2ϩ channels, but less than that caused by Ca 2ϩ influx through N-type channels. Our results indicate that exocytosis may be regulated even in excitable cells by Ca 2ϩ influx through pathways other than voltage-gated Ca 2ϩ channels.

Estradiol Inhibits Depolarization-Evoked Exocytosis in PC12 Cells via N-Type Voltage-Gated Calcium Channels

“…Exocytosis initiated by depolarization with K ? depends primarily on L-and N-type VGCCs in PC12 cells (Taylor and Peers 1999). We used the specific N-type VGCC antagonist, x-conotoxin GVIA (Hirning et al 1988), to test whether the action of E2 on N-type VGCCs was sufficient to account for its inhibition of exocytosis.…”

“…PC12 cells secrete dopamine from large dense-core vesicles, permitting detection of individual vesicle release events with carbon fiber amperometry (Chen et al 1994;Westerink and Ewing 2008). They have been used as a model system to study both voltage-gated calcium channels (VGCCs) and intracellular calcium release mechanisms (Bennett et al 1998;Taylor and Peers 1999;Tully and Treistman 2004). Importantly, PC12 cells are also an appropriate model system to study the effects of estrogens.…”

Effects of (1R,9S)-.BETA.-Hydrastine on Intracellular Calcium Concentration in PC12 Cells

“…A high extracellular K ϩ level produces membrane depolarization in excitable, neuronal and PC12, cells and causes a rapid increase in [Ca 2ϩ ] i along with the release of neurotransmitters such as dopamine through the voltage-gated Ca 2ϩ channels. 10,11) In addition, [Ca 2ϩ ] i is regulated by Ca 2ϩ uptake and leakage from the endoplasmic reticulum (ER). The uptake of Ca 2ϩ is mediated by the Ca 2ϩ pump, sarco (endo)-plasmic reticulum Ca 2ϩ ATPases (SERCA).…”

Vesicular Catecholamine Release from Rat PC12 Cells on Acute and Subchronic Exposure to Polychlorinated Biphenyls

“…Conversely, a decrease of dopamine availability by inhibition of tyrosine hydroxylase and by inhibition of dopamine transport across the plasma membrane (Pothos and Sulzer, 1998) is associated with a decrease in vesicle contents. In addition, a disturbance in Ca 2ϩ homeostasis, e.g., induced by caffeine in PC12 cells (Taylor and Peers, 1999), may lead to changes in basal release.The combined literature data indicate that PCBs will exert a general effect on the probability of vesicle exocytosis and a more specific effect on the contents of catecholamine-containing vesicles. The effects two ortho-substituted nonplanar congeners [PCB 4 and 2,2Ј,3,3Ј,4,4Ј-hexachlorobiphenyl (PCB 128)] and one coplanar congener [3,3Ј,4,4Ј,5-pentachlorobiphenyl (PCB 126)] on vesicular catecholamine release from single PC12 cells were investigated.…”

“…Conversely, a decrease of dopamine availability by inhibition of tyrosine hydroxylase and by inhibition of dopamine transport across the plasma membrane (Pothos and Sulzer, 1998) is associated with a decrease in vesicle contents. In addition, a disturbance in Ca 2ϩ homeostasis, e.g., induced by caffeine in PC12 cells (Taylor and Peers, 1999), may lead to changes in basal release.…”