Role of Cytosolic Calcium in Vasopressin-sensitive Epithelia

Taylor, Ann; Pearl, M.; Barber, B; Crutch, Beth

doi:10.1007/978-1-4612-5284-9_5

Cited by 4 publications

(8 citation statements)

References 22 publications

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“…Similar results were obtained using 30 /~M ionomycin, except that signal saturation at low Fura 2 content was not observed. When lower concentrations of ionophores were tested, either transient or small stable increases in Caf were observed consistent with previous studies in a variety of cell types [18,31,36,41]. When either ionophore was added to cells in the presence of 5 mM EGTA, no consis- Medium Na (mM) Control Caf { nM) Fig.…”

Section: Resultssupporting

confidence: 81%

“…At higher Quin 2 loading (50-180 nmol/mg protein), an apparent minimum value for Casof 58 _+ 8.4 nM (n = 8) was observed, a value consistent with Ca s measured in Quin 2 loaded toad bladder cells incubated in medium containing 0.1 mM Ca [36]. Conversely, at low Fura 2 loading (0.05-0.2 nmol/mg protein), no clear plateau value for Caf was observed.…”

Section: Discussionsupporting

confidence: 68%

“…The apparent Km for the effect of medium sodium on Caf was 10-20 mM. Previous studies in toad bladder cells [36,47], cultured epithelial cells [6,35], rabbit proximal tubules [26] and Necturus proximal tubule [24] have also reported an increase in Ca s following Na substitution. While increased Caf has been interpreted as evidence for Na-Ca exchange mediated Ca efflux, the use of nonpolarized cell suspensions in the present study makes this conclusion tenuous.…”

Section: Resultsmentioning

confidence: 76%

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Fluorescent measurements of intracellular free calcium in isolated toad urinary bladder epithelial cells

Jacobs

Mandel

1987

J. Membrain Biol.

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Sodium-calcium exchange has been suggested to play a pivotal role in the regulation of cytosolic free calcium (Caf) by epithelial cells. Using isolated epithelial cells from the toad urinary bladder, Caf has been measured using the intracellular Ca-sensitive fluorescent dyes Fura 2 and Quin 2. Dye loading did not alter cell viability as assessed by measurements of ATP and ADP content or cell oxygen consumption. When basal Caf was examined over a wide range of cell dye content (from 0.04 to 180 nmol dye/mg protein) an inverse relationship was observed. At low dye content, Caf was 300-380 nM and, as dye content was increased, Caf progressively fell to 60 nM. Using low dye content cells, in which minimal alteration in Ca steady state would be expected, the role for plasma membrane Na-Ca exchange was examined using either medium sodium substitution or ouabain. While medium sodium substitution increased Caf, prolonged treatment with ouabain had no effect on Caf despite a clear increase in cell sodium content. The lack of effect of ouabain suggests that Na-Ca exchange-mediated Ca efflux plays a minimal role in the regulation of basal Caf. However, exchange-mediated Ca efflux may play a role in Caf regulation when cytosolic calcium is elevated.

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Section: Resultssupporting

confidence: 81%

Section: Discussionsupporting

confidence: 68%

Section: Resultsmentioning

confidence: 76%

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Fluorescent measurements of intracellular free calcium in isolated toad urinary bladder epithelial cells

Jacobs

Mandel

1987

J. Membrain Biol.

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“…Under the influence of vasopressin, aggrephores fuse with the apical plasma membrane (Muller, Kachadorian & DiScala, 1980), when they can be seen as parallel-sided fusion profiles in thin-section electron micrographs. The translocation of aggrephores towards the plasma membrane is believed to occur along microtubules; this translocation is presumed to be driven by a microtubule-based motor, such as dynein (Taylor, Pearl, Marples, Phillips, Turner & Ahrens, 1993). Microfilaments may be involved in the movement of the particle aggregates out of the fused aggrephores onto the cell surface (Muller et al 1980).…”

Section: Introductionmentioning

confidence: 99%

Activation of the vasopressin‐sensitive water permeability pathway in the toad bladder by N‐ethyl maleimide

Marples¹,

Bourguet²,

Taylor³

1994

Experimental Physiology

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SUMMARYVasopressin stimulates transepithelial water flow in the toad urinary bladder. We report here that N-ethyl maleimide (NEM) (0-1 mM) produces a similar increase in osmotic water flow when applied to the mucosal surface of the tissue. NEM-induced water flow is sensitive to inhibitors of hormone-induced water flow, including serosal acidification, or exposure to quinidine or cytoskeleton-disruptive drugs. NEM-induced water flow is additive with that induced by a submaximal, but not a maximal, dose of vasopressin. The response to mucosal NEM is not reversed on removal of the reagent, but established NEM-induced water flow can be inhibited by serosal acidification or quinidine. Like vasopressin, mucosal NEM induces the appearance of fusion profiles and intramembranous particle aggregates (putative water channels) in the apical plasma membrane of the granular cells, and the incidence of particle aggregates correlates with water flow. NEM does not cause an increase in intracellular cAMP.Our data suggest that NEM stimulates transepithelial water flow by irreversibly activating cellular mechanisms normally triggered by vasopressin, hence causing the insertion of water channels.

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“…We have recently demonstrated that the microtubule-disruptive agents, nocodazole and colcemid, specifically inhibit the initiation of the hydrosmotic respone to VP or exogenous cAMP in isolated rabbit collecting tubules (Phillips & Tauylor, 1987, 1989. We now report experiments with taxol, an antimitotic agent which binds to intact microtubules and induces abnormal assembly of microtubules in cells (Manfredi et al 1982), and which has been shown to inhibit VP-stimulated water flow in the toad bladder (Taylor et al 1982).…”

Section: Pmentioning

confidence: 99%

Proceedings of the Physiological Society, 30 June‐ 1 July 1989, Oxford Meeting: Communications

1989

The Journal of Physiology

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Impaired autoregulation of cerebral blood flow has been implicated as a major aetiological factor for intraventricular haemorrhage and cerebral ischaemia in preterm infants (Lou & Lassen, 1979). The purpose of this study was to determine the degree of cerebral autoregulation in high-risk preterm infants.Simultaneous beat to beat measurements of cerebral blood flow velocity from the middle cerebral artery and mean intra-arterial blood pressure were made in 83 preterm infants (gestational age 24-36 weeks, birth weight 565-2750 g, age 1-2 days). The velocity measurements were obtained using the Vingmed CFM700 ultrasound unit interfaced to a computer. These data were stored using BVA (Andiamo A/S, Oslo, Norway) data acquisition system which also stored mean arterial pressure and heart rate. The recordings were 1-3 min long, and made when the infants were in a stable clinical condition, with normal blood gases. Records where spontaneous alterations in blood pressure of more than 10% of the resting level occurred without significant alteration in heart rate were used for the analysis. The percentage change in blood velocity per mmHg blood pressure was determined for each baby. In 23 babies the percentage change was less than 2 %/mmHg (not significant), in 33 babies between 2 and 8 %/mmHg and in 10 babies greater than 8 %/mmHg. In 17 babies insufficient alteration in blood pressure made analysis unsatisfactory. All babies over 32 weeks gestation were in the first group and all babies under 28 weeks were in the last two groups. Between 28 and 32 weeks gestation there was a fairly even distribution between the groups. All babies with severe intracranial lesions on early serial ultrasound scan had changes greater than 2 %/mmHg. However, half the babies with normal scans also had changes greater than 2 %/mmHg.These findings indicate that cerebral autoregulation is gestational age dependent and poorly developed below 28 weeks gestation. However, many babies over this age also do not regulate well but this does not necessarily lead to the development of severe intracranial pathology.

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Role of Cytosolic Calcium in Vasopressin-sensitive Epithelia

Cited by 4 publications

References 22 publications

Fluorescent measurements of intracellular free calcium in isolated toad urinary bladder epithelial cells

Fluorescent measurements of intracellular free calcium in isolated toad urinary bladder epithelial cells

Activation of the vasopressin‐sensitive water permeability pathway in the toad bladder by N‐ethyl maleimide

Proceedings of the Physiological Society, 30 June‐ 1 July 1989, Oxford Meeting: Communications

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