Calcium-dependent regulation of cholecystokinin secretion and potassium currents in STC-1 cells

Abstract

Secretory and electrophysiological properties of STC-1 cells, a cholecystokinin-secreting cell line, were examined with a radioimmunoassay and patch-clamp recording techniques. Stimulation of cholecystokinin secretion was seen after exposure to agents anticipated to increase the level of intracellular calcium, including thapsigargin (8 microM), bombesin (50 nM), potassium-induced depolarization (50 mM), or after blockade of potassium channels with barium chloride (2 mM). The secretory effects of these agents were blocked by pretreatment with the calcium channel blocker diltiazem (1 microM). Whole cell patch-clamp recordings showed a hyperpolarizing shift in reversal potential after exposure to either thapsigargin (8 microM) or bombesin (50 nM) from a control value of -27 +/- 3 to -57 +/- 7 or -48 +/- 6 mV, respectively. This shift was in the direction of the reversal potential for potassium and was blocked by barium chloride (5 mM). Single-channel recordings from cell-attached membrane patches showed an inwardly rectifying potassium channel with channel open probability modulated by bombesin. These results indicate that in STC-1 cells a potassium current is increased by agents that stimulate CCK secretion, presumably by increasing the level of cytosolic calcium. STC-1 cells may serve as a model system to study the electrophysiological and secretory mechanisms involved in the release of cholecystokinin.

Studies with GIP/Ins cells indicate secretion by gut K cells is KATPchannel independent

“…This conclusion is consistent with our in vivo immunohistochemical studies indicating that gut L cells, like gut K cells, do not express detectable Kir 6.1 or Kir 6.2. Patch-clamp studies have also demonstrated the presence of K ATP channels in parent STC-1 cells (2,28,30,58). Thus it has been proposed that they play a role in regulating CCK secretion (2,27,28).…”

“…All cells were cultured in an atmosphere of 5% CO2-95% air and 100% humidity. MIN6 cells (passage [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] were cultured in DMEM containing 15% FCS, as previously described (39,67), and GIP/Ins cells were cultured in DMEM containing 10% FCS (39).…”

The extracellular calcium-sensing receptor is required for cholecystokinin secretion in response to l-phenylalanine in acutely isolated intestinal I cells

“…ATP-sensitive K ϩ channels regulating basal membrane potential (20,23) can be affected by CaSR. However, there was no difference in basal secretion between CaSR WT and KO CCK-eGFP cells.…”

Immunoglobulin-like domain containing receptor 1 mediates fat-stimulated cholecystokinin secretion

“…Several physiological secretagogues (such as monitor peptide and amino acids) as well as exposure to depolarizing concentrations of KCl increase [Ca 2+ ] i , which is linked to hormone release (7,8,23,24). In this study, involvement of calcium signaling in ILDR1-stimulated CCK secretion was demonstrated by comparing [Ca 2+ ] i in wild-type and Ildr1 -/-CCK-EGFP cells.…”

“…Changes in intracellular calcium concentrations are critically important for regulated CCK secretion (23,24). Figure 6), suggesting that these cells were capable of responding to amino acid stimulation.…”