Hormonal activation of single K<sup>+</sup> channels via internal messenger in isolated pancreatic acinar cells

Suzuki, Kazuo; Petersen, Carl C. H.; Petersen, Ole H.

doi:10.1016/0014-5793(85)80131-9

Cited by 28 publications

(12 citation statements)

References 18 publications

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“…The spontaneous resting potential in this condition was about -30 mV and outward K+ currents were activated by depolarizing voltage jumps whereas hyperpolarizing jumps evoked much smaller inward currents. Pentagastrin (10-6 M) increased the outward K+ current as previously demonstrated in pig pancreatic acinar cells (Suzuki et al 1985) but also enhanced the inward current.…”

Section: Psupporting

confidence: 80%

“…The dominating low-conductance K+ channel was also studied in cell-attached membrane patches. At the spontaneous membrane potential (about -40 to -50 mV) there were only few channel openings, but addition of pentagastrin to the bath (10-6 M) increased the frequency of channel openings as previously described for the highconductance channel in pig pancreatic acinar cells (Suzuki, Petersen & Petersen, 1985).…”

Section: Psupporting

confidence: 68%

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Proceedings of the Physiological Society, 18‐19 April 1986, Sheffield Meeting: Communications

1986

The Journal of Physiology

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The effect of ileal infusion of lipid on the motility pattern in humans after ingestion of a viscous, non-nutrient meal By I. McL. WELCH and J. WORLDING (introduced by N. W. READ). Sub-Department of Human Gastrointestinal Physiology and Nutrition, The University, Sheffield 510 2T1 Previous studies have shown that an ileal infusion of lipid delays gastric emptying and slows small-bowel transit time in humans. The effects of ileal lipid on intestinal motility are however unclear. The aim of this study was to document the effect of ileal lipid on jejunal motor activity in eight healthy volunteers.Intrfluminal pressure changes were continuously recorded at seven sites, 4 cm apart, in the jejunum (the most proximal port located 100 cm from the teeth) following ingestion of a 300 ml, 40 guar gum meal, flavoured with diabetic orange squash. Isosmotic saline was infused into the distal ileum at a rate of 1 ml/min throughout the recording period (120 min), except for a 20 min infusion of 200% Intralipid, which commenced 30 min after ingestion of the test meal. Four of the eight subjects also completed a control study during which isosmotic saline was infused throughout the experiment.Ingestion of the guar gum meal induced a fed motility pattern in all 12 studies. Seven studies showed discrete clusters of contractions (3-15 in number) interspersed by periods of quiescence coordinated, and in many instances propagated through all seven pressure ports. One study showed irregular contractions through all the recording sites. Four studies showed a mixture of both irregular and clustered contractions.Ileal infusion of Intralipid in all eight subjects appeared to alter the postprandial motility pattern, leading to: a decrease in amplitude and frequency of contractions;or a reduction in the coordination of contraction clusters; or a reduction in the degree of propagation of coordinated contraction clusters; or a combination of these effects.No such alteration of motor activity was observed at similar times in the control experiments. A pattern resembling phase III of the migrating motor complex was observed within 120 min of ingestion of the meal in 3 out of 4 control studies but only in 2 out of 8 intralipid studies.In conclusion, infusion of lipid into the ileum alters motor activity in the jejunum in a manner that could account for a delay in small-bowel transit time.The protocol for this study was approved by the Ethical Sub-committee of the Sheffield Area Health Authority. The motor activity of the human pylorus and the role it plays in regulating gastric emptying is poorly defined. We have recorded pyloric pressures in 15 normal volunteers after they had ingested a meal of liver hamburger (100 g) with 200 ml of either normal saline (8 volunteers) or 25 % dextrose in normal saline (7 volunteers).Both solid and liquid phases were labelled with radioisotopes. Pyloric pressure was recorded using a sleeve sensor 4-5 cm long positioned by measuring the transmucosal p.d. at either end of the sleeve. Pressures were also measured a...

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Section: Psupporting

confidence: 80%

Section: Psupporting

confidence: 68%

Proceedings of the Physiological Society, 18‐19 April 1986, Sheffield Meeting: Communications

1986

The Journal of Physiology

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“…Basolateral Ca2+-activated K + channels have been found in the salivary gland and pancreas (Maruyama et al, 1983;Susuki et al, 1985). There is as yet no evidence for cAMP-regulated K + channels, but cAMP may not be important in zymogen secretion in these tissues.…”

Section: Voltage Dependence Of Opening and Closingmentioning

confidence: 96%

Regulation of K+ channels in the basolateral membrane ofNecturus oxyntic cells

1987

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Patch-clamp methods were used to study single-channel events in isolated oxyntic cells and gastric glands from Necturus maculosa. Cell-attached, excised inside-out and outside-out patches from the basolateral membrane frequently contained channels which had conductances of 67 +/- 21 pS in 24% of the patches and channels of smaller conductance, 33 +/- 6 pS in 56% of the patches. Channels in both classes were highly selective for K+ over Na+ and Cl-, and shared linear current-voltage relations. The 67-pS channel was activated by membrane depolarization, whereas the activity of the 33-pS channel was relatively voltage independent. The larger conductance channels were activated by intracellular Ca2+ in the range between 5 and 500 nM, but unaffected by cAMP. The smaller conductance channels were activated by cAMP, but not Ca2+. The presence of K+ channels in the basolateral membrane which are regulated by these known "second messengers" can account for the increase in conductance and the hyperpolarization of the membrane observed upon secretagogue stimulation.

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“…The agonist-initiated effiuxes were affected differently by inhibitors of K + channels (Table I). The maximum rate of the ATP-promoted K + effiux was reduced by -30% by TEA (15 mM), which blocks the BK (or maxi K) channel (Iwatsuki and Petersen, 1985;Suzuki et al, 1985). TEA was almost twice as effective in reducing the carbachol-stimulated effiux (Soitoff et al, 1989;and Table I).…”

Section: Effects Of Inhibitors On K + Effluxmentioning

confidence: 99%

Effects of extracellular ATP on ion transport systems and [Ca2+]i in rat parotid acinar cells. Comparison with the muscarinic agonist carbachol.

Soltoff

McMillian

Cragoe

et al. 1990

The Journal of General Physiology

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The effects of extracellular ATP on ion fluxes and the intracellular free Ca 2 § concentration ([Ca~+]i) were examined using a suspension of rat parotid acinar cells and were contrasted with the effects of the muscarinic agonist carbachol. Although ATP and carbachol both rapidly increased [Ca2+] i about threefold above the resting level (200-250 nM), the effect of ATP was due primarily to an influx of Ca ~+ across the plasma membrane, while the initial response to carbachol was due to a release of Ca ~ § from intracellular stores. Within 10 s, ATP (1 mM) and carbachol (20 #M) reduced the cellular C1-content by 39-50% and cell volume by 15-25%. Both stimuli reduced the cytosolic K + content by 57-65%, but there were marked differences in the rate and pattern of net K § movement as well as the effects of K + channel inhibitors on the effluxes initiated by the two stimuli. The maximum rate of the ATP-stimulated K § efflux (~2,200 nmol K+/mg protein per min) was about two-thirds that of the carbachol-initiated efflux rate, and was reduced by ~30% (vs. 60% for the carbachol-stimulated K + efflux) by TEA (tetraethylammonium), an inhibitor of the large conductance (BK) K § channel. Charybdotoxin, another K § channel blocker, was markedly more effective than TEA on the effects of both agonists, and reduced the rate of K § effiux initiated by both ATP and carbachol by ~80%. The removal of extracellular Ca ~ § reduced the ATPand the carbachol-stimulated rates of K + efflux by 55 and 17%, respectively. The rate of K + effiux initiated by either agonist was reduced by 78-95% in cells that were loaded with BAPTA to slow the elevation of [Ca2+]i. These results indicated that ATP and carbachol stimulated the effiux of K + through multiple types of K § permeable channels, and demonstrated that the relative proportion of efflux 320THE JOURNAL OF GENERAL PHYSIOLOGY 9 VOLUME 95 9 1990 through the different pathways was different for the two stimuli. ATP and carbachol also stimulated the rapid entry of Na § into the parotid cell, and elevated the intracellular Na § content to 4.4 and 2.6 times the normal level, respectively. The rate of Na § entry through Na+-K+-2CI-cotransport and Na+-H § exchange was similar whether stimulated by ATP, carbachol, or ionomycin, and uptake through these two carrier-mediated transporters accounted for 50% of the ATP-promoted Na § influx. The remainder may be due to a nonselective cation channel and an ATP-gated cation channel that is also permeable to Ca ~ § The consumption of extracellular ATP by an ecto-ATPase (apparent K0.5 for ATP is 0.93 mM) on the plasma membrane limited the duration of the response to ATP when large concentrations of cells were used. The effects of ATP on [Ca~+]i and ion fluxes were blocked specifically by DIDS (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid), and were more potent in the absence of Mg ~+, suggesting that the active nucleotide moiety was ATP 4-. These studies suggest that ATP may function as a neurotransmitter and modulate fluid secretion by stimula...

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Hormonal activation of single K⁺ channels via internal messenger in isolated pancreatic acinar cells

Cited by 28 publications

References 18 publications

Proceedings of the Physiological Society, 18‐19 April 1986, Sheffield Meeting: Communications

Proceedings of the Physiological Society, 18‐19 April 1986, Sheffield Meeting: Communications

Regulation of K+ channels in the basolateral membrane ofNecturus oxyntic cells

Effects of extracellular ATP on ion transport systems and [Ca2+]i in rat parotid acinar cells. Comparison with the muscarinic agonist carbachol.

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Hormonal activation of single K+ channels via internal messenger in isolated pancreatic acinar cells

Cited by 28 publications

References 18 publications

Proceedings of the Physiological Society, 18‐19 April 1986, Sheffield Meeting: Communications

Proceedings of the Physiological Society, 18‐19 April 1986, Sheffield Meeting: Communications

Regulation of K+ channels in the basolateral membrane ofNecturus oxyntic cells

Effects of extracellular ATP on ion transport systems and [Ca2+]i in rat parotid acinar cells. Comparison with the muscarinic agonist carbachol.

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Hormonal activation of single K⁺ channels via internal messenger in isolated pancreatic acinar cells