Endogenous H2S is required for hypoxic sensing by carotid body glomus cells

H2S generated by the enzyme cystathionine-γ-lyase (CSE) has been implicated in O2 sensing by the carotid body. The objectives of the present study were to determine whether glomus cells, the primary site of hypoxic sensing in the carotid body, generate H2S in an O2-sensitive manner and whether endogenous H2S is required for O2 sensing by glomus cells. Experiments were performed on glomus cells harvested from anesthetized adult rats as well as age and sex-matched CSE+/+ and CSE−/− mice. Physiological levels of hypoxia (Po2 ∼30 mmHg) increased H2S levels in glomus cells, and dl-propargylglycine (PAG), a CSE inhibitor, prevented this response in a dose-dependent manner. Catecholamine (CA) secretion from glomus cells was monitored by carbon-fiber amperometry. Hypoxia increased CA secretion from rat and mouse glomus cells, and this response was markedly attenuated by PAG and in cells from CSE−/− mice. CA secretion evoked by 40 mM KCl, however, was unaffected by PAG or CSE deletion. Exogenous application of a H2S donor (50 μM NaHS) increased cytosolic Ca2+ concentration ([Ca2+]i) in glomus cells, with a time course and magnitude that are similar to that produced by hypoxia. [Ca2+]i responses to NaHS and hypoxia were markedly attenuated in the presence of Ca2+-free medium or cadmium chloride, a pan voltage-gated Ca2+ channel blocker, or nifedipine, an L-type Ca2+ channel inhibitor, suggesting that both hypoxia and H2S share common Ca2+-activating mechanisms. These results demonstrate that H2S generated by CSE is a physiologic mediator of the glomus cell's response to hypoxia.

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Intracerebroventricular injection of prostaglandin E2 increases splenic sympathetic nerve activity in rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1995.269.3.r662 ◽

1995 ◽

Vol 269 (3) ◽

pp. R662-R668 ◽

Cited By ~ 5

Author(s):

T. Ando ◽

T. Ichijo ◽

T. Katafuchi ◽

T. Hori

Keyword(s):

Prostaglandin E2 ◽

Sympathetic Nerve ◽

Time Course ◽

Sympathetic Nerve Activity ◽

Dependent Manner ◽

Central Administration ◽

Nerve Activity ◽

High Doses ◽

Alpha Chloralose ◽

Dose Dependent

The effects of central administration of prostaglandin E2 (PGE2) and its selective agonists on splenic sympathetic nerve activity (SNA) were investigated in urethan- and alpha-chloralose-anesthetized rats. An intra-third-cerebroventricular (13V) injection of PGE2 (0.1-10 nmol/kg) increased splenic SNA in a dose-dependent manner. An I3V injection of an EP1 agonist, 17-phenyl-omega-trinor PGE2 (1-30 nmol/kg), also resulted in a dose-dependent increase in splenic SNA, with a time course similar to that of PGE2-induced responses. In contrast, EP2 agonists, butaprost (10-100 nmol/kg I3V) and 11-deoxy-PGE1 (10-100 nmol/kg I3V), had no effect on splenic SNA. An I3V injection of M & B-28767 (an EP3/EP1 agonist, EP3 >> EP1) increased splenic SNA only at high doses (10-100 nmol/kg). Pretreatment with an EP1 antagonist, SC-19220 (200 and 500 nmol/kg), completely blocked the responses of splenic SNA to PGE2 (0.1 nmol/kg) and M & B-28767 (10 nmol/kg), respectively. These findings indicate that brain PGE2 increases splenic SNA through its action on EP1 receptors.

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Effect of remving [Ca2+]o on anoxia-induced [Ca2+]i increase in cultured carotid body glomus cells of newborn rabbits

Neuroscience Research Supplements ◽

10.1016/0921-8696(94)92333-7 ◽

1994 ◽

Vol 19 ◽

pp. S26

Author(s):

Minoru Sato ◽

Masahito Kawatani

Keyword(s):

Carotid Body ◽

Glomus Cells ◽

Carotid Body Glomus Cells

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Developmental Aspects of Carotid Body Glomus Cells

Histochemistry and Cell Biology of Autonomic Neurons and Paraganglia ◽

10.1007/978-3-642-72749-8_36 ◽

1987 ◽

pp. 208-212

Author(s):

J. T. Hansen

Keyword(s):

Carotid Body ◽

Glomus Cells ◽

Carotid Body Glomus Cells

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Effects of pinacidil on coronary Ca2+-myosin phosphorylation in cold potassium cardioplegia model

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2000.279.3.h882 ◽

2000 ◽

Vol 279 (3) ◽

pp. H882-H888 ◽

Cited By ~ 2

Author(s):

Naruto Matsuda ◽

Kathleen G. Morgan ◽

Frank W. Sellke

Keyword(s):

Time Course ◽

Dependent Manner ◽

Coronary Smooth Muscle ◽

Intracellular Ca ◽

No Signaling ◽

Synthase Inhibitor ◽

Mlc Phosphorylation ◽

Dose Dependent ◽

Cardioplegic Solutions

The effects of the potassium (K+) channel opener pinacidil (Pin) on the coronary smooth muscle Ca2+-myosin light chain (MLC) phosphorylation pathway under hypothermic K+cardioplegia were determined by use of an in vitro microvessel model. Rat coronary arterioles (100–260 μm in diameter) were subjected to 60 min of simulated hypothermic (20°C) K+cardioplegic solutions (K+= 25 mM). We first characterized the time course of changes in intracellular Ca2+concentration, MLC phosphorylation, and diameter and observed that the K+cardioplegia-related vasoconstriction was associated with an activation of the Ca2+-MLC phosphorylation pathway. Supplementation with Pin effectively suppressed the Ca2+accumulation and MLC phosphorylation in a dose-dependent manner and subsequently maintained a small decrease in vasomotor tone. The ATP-sensitive K+(KATP)-channel blocker glibenclamide, but not the nitric oxide (NO) synthase inhibitor Nω-nitro-l-arginine methyl ester, significantly inhibited the effect of Pin. K+cardioplegia augments the coronary Ca2+-MLC pathway and results in vasoconstriction. Pin effectively prevents the activation of this pathway and maintains adequate vasorelaxation during K+cardioplegia through a KATP-channel mechanism not coupled with the endothelium-derived NO signaling cascade.

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Nitric Oxide Inhibits L-Type Ca2+ Current in Glomus Cells of the Rabbit Carotid Body Via a cGMP-Independent Mechanism

Journal of Neurophysiology ◽

10.1152/jn.1999.81.4.1449 ◽

1999 ◽

Vol 81 (4) ◽

pp. 1449-1457 ◽

Cited By ~ 97

Author(s):

Beth A. Summers ◽

Jeffrey L. Overholt ◽

Nanduri R. Prabhakar

Keyword(s):

Nitric Oxide ◽

Carotid Body ◽

Channel Blocker ◽

Adult Rabbit ◽

Subsequent Formation ◽

No Donors ◽

Glomus Cells ◽

Channel Proteins ◽

Carotid Bodies ◽

Independent Mechanism

Nitric oxide inhibits L-type Ca2+ current in glomus cells of the rabbit carotid body via a cGMP-independent mechanism. Previous studies have shown that nitric oxide (NO) inhibits carotid body sensory activity. To begin to understand the cellular mechanisms associated with the actions of NO in the carotid body, we monitored the effects of NO donors on the macroscopic Ca2+ current in glomus cells isolated from rabbit carotid bodies. Experiments were performed on freshly dissociated glomus cells from adult rabbit carotid bodies using the whole cell configuration of the patch-clamp technique. The NO donors sodium nitroprusside (SNP; 600 μM, n = 7) and spermine nitric oxide (SNO; 100 μM, n = 7) inhibited the Ca2+ current in glomus cells in a voltage-independent manner. These effects of NO donors were rapid in onset and peaked within 1 or 2 min. In contrast, the outward K+ current was unaffected by SNP (600 μM, n = 6), indicating that the inhibition by SNP was not a nonspecific membrane effect. 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (carboxy-PTIO; 500 μM), an NO scavenger, prevented inhibition of the Ca2+ current by SNP ( n = 7), whereas neither superoxide dismutase (SOD; 2,000 U/ml, n = 4), a superoxide scavenger, nor sodium hydrosulfite (SHS; 1 mM, n = 7), a reducing agent, prevented inhibition of the Ca2+ current by SNP. However, SNP inhibition of the Ca2+ current was reversible in the presence of either SOD or SHS. These results suggest that NO itself inhibits Ca2+current in a reversible manner and that subsequent formation of peroxynitrites results in irreversible inhibition. SNP inhibition of the Ca2+ current was not affected by 30 μM LY 83,583 ( n = 7) nor was it mimicked by 600 μM 8-bromoguanosine 3′:5′-cyclic monophosphate (8-Br-cGMP; n = 6), suggesting that the effects of NO on the Ca2+ current are mediated, in part, via a cGMP-independent mechanism. N-ethylmaleimide (NEM; 2.5 mM, n= 6) prevented the inhibition of the Ca2+ current by SNP, indicating that SNP is acting via a modification of sulfhydryl groups on Ca2+ channel proteins. Norepinephrine (NE; 10 μM) further inhibited the Ca2+ current in the presence of NEM ( n = 7), implying that NEM did not nonspecifically eliminate Ca2+ current modulation. Nisoldipine, an L-type Ca2+ channel blocker (2 μM, n = 6), prevented the inhibition of Ca2+ current by SNP, whereas ω-conotoxin GVIA, an N-type Ca2+ channel blocker (1 μM, n = 9), did not prevent the inhibition of Ca2+ current by SNP. These results demonstrate that NO inhibits L-type Ca2+ channels in adult rabbit glomus cells, in part, due to a modification of calcium channel proteins. The inhibition might provide one plausible mechanism for efferent inhibition of carotid body activity by NO.

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Ca2+ Current in Rabbit Carotid Body Glomus Cells Is Conducted by Multiple Types of High-Voltage–Activated Ca2+ Channels

Journal of Neurophysiology ◽

10.1152/jn.1997.78.5.2467 ◽

1997 ◽

Vol 78 (5) ◽

pp. 2467-2474 ◽

Cited By ~ 48

Author(s):

Jeffrey L. Overholt ◽

Nanduri R. Prabhakar

Keyword(s):

High Voltage ◽

Carotid Body ◽

Neurotransmitter Release ◽

Relative Proportion ◽

Sensory Transduction ◽

Arterial Oxygen ◽

Patch Clamp Technique ◽

Simultaneous Application ◽

Glomus Cells ◽

Carotid Body Glomus Cells

Overholt, Jeffrey L. and Nanduri R. Prabhakar. Ca2+ current in rabbit carotid body glomus cells is conducted by multiple types of high-voltage–activated Ca2+ channels. J. Neurophysiol. 78: 2467–2474, 1997. Carotid bodies are sensory organs that detect changes in arterial oxygen. Glomus cells are presumed to be the initial sites for sensory transduction, and Ca2+-dependent neurotransmitter release from glomus cells is believed to be an obligatory step in this response. Some information exists on the Ca2+ channels in rat glomus cells. However, relatively little is known about the types of Ca2+ channels present in rabbit glomus cells, the species in which most of the neurotransmitter release studies have been performed. Therefore we tested the effect of specific Ca2+ channel blockers on current recorded from freshly dissociated, adult rabbit carotid body glomus cells using the whole cell configuration of the patch-clamp technique. Macroscopic Ba2+ current elicited from a holding potential of −80 mV activated at a V m of approximaely −30 mV, peaked between 0 and +10 mV and did not inactivate during 25-ms steps to positive test potentials. Prolonged (≈2 min) depolarized holding potentials inactivated the current with a V 1/2 of −47 mV. There was no evidence for T-type channels. On steps to 0 mV, 6 mM Co2+ decreased peak inward current by 97 ± 1% (mean ± SE). Nisoldipine (2 μM), 1 μM ω-conotoxin GVIA, and 100 nM ω-agatoxin IVa each blocked a portion of the macroscopic Ca2+ current (30 ± 5, 33 ± 5, and 19 ± 3% after rundown correction, respectively). Simultaneous application of these blockers revealed a resistant current that was not affected by 1 μMω-conotoxin MVIIC. This resistant current constituted 27 ± 5% of the total macroscopic Ca2+ current. Each blocker had an effect in every cell so tested. However, the relative proportion of current blocked varied from cell to cell. These results suggest that L, N, P, and resistant channel types each conduct a significant proportion of the macroscopic Ca2+ current in rabbit glomus cells. Hypoxia-induced neurotransmitter release from glomus cells may involve one or more of these channels.

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Effect of cocaine and methylecgonidine on intracellular Ca2+ and myocardial contraction in cardiac myocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1997.273.2.h893 ◽

1997 ◽

Vol 273 (2) ◽

pp. H893-H901 ◽

Cited By ~ 1

Author(s):

L. Huang ◽

J. H. Woolf ◽

Y. Ishiguro ◽

J. P. Morgan

Keyword(s):

Structural Damage ◽

Time Course ◽

Crack Cocaine ◽

Pyrolysis Product ◽

Myocardial Contraction ◽

Dependent Manner ◽

Response Curves ◽

Inotropic Effects ◽

Cell Shortening ◽

Dose Dependent

We evaluated the cardiac effects of the principle pyrolysis product of crack cocaine smoking, methylecgonidine (MEG), in comparison with cocaine. Peak cell shortening and intracellular Ca2+, as detected by the Ca2+ indicator indo 1, were recorded in enzymatically isolated ferret myocytes. Both cocaine and MEG decreased peak cell shortening and peak intracellular Ca2+ concentration ([Ca2+]i) in a dose-dependent manner (10(-8)-10(-4) M). MEG shifted the peak [Ca2+]i-to-peak shortening relationship downward and was more potent than cocaine. Atropine (10(-6) M) upwardly shifted the dose-response curves of MEG, cocaine, and carbachol but not of procaine. The negative inotropic effects of MEG were inhibited by methoctramine, a selective M2 receptor blocker but not by M1 (pirenzepine) or M3 (4-diphenylacetoxy-N-methylpiperidine methiodide) blocking agents. In contrast to cocaine, the effects of large doses of MEG were irreversible over the time course of our experiments, raising the possibility of structural damage. We conclude that MEG acts primarily on M2 cholinergic receptors in the heart to produce acute cardiac intoxication and, in contrast to cocaine, may decrease the myofilament Ca2+ responseness and cause structural damage to myocytes by a direct toxic effect.

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Effect of sphingosine derivatives on calcium fluxes in thyroid FRTL-5 cells

Biochemical Journal ◽

10.1042/bj2990213 ◽

1994 ◽

Vol 299 (1) ◽

pp. 213-218 ◽

Cited By ~ 19

Author(s):

K Törnquist ◽

E Ekokoski

Keyword(s):

Elevated Level ◽

Channel Blocker ◽

Thyroid Stimulating Hormone ◽

Thyroid Cell ◽

Dependent Manner ◽

Myristate Acetate ◽

Permeabilized Cells ◽

Inositol 1,4,5 Trisphosphate ◽

Dose Dependent ◽

In Cells

The effects of sphingosine derivatives on Ca2+ fluxes were investigated in thyroid FRTL-5 cells labelled with Fura 2. Addition of sphingosylphosphocholine (SPC) or sphingosine (SP) increased intracellular free Ca2+ ([Ca2+]i) in a dose-dependent manner. At the highest dose tested (30 microM), the response was biphasic: a rapid transient increase in [Ca2+]i, followed by a new, elevated, level of [Ca2+]i. Both phases of the SPC-evoked increase in [Ca2+]i were dependent on extracellular Ca2+, whereas only the SP-evoked elevated level of [Ca2+]i was dependent on the influx of Ca2+. Both compounds released sequestered Ca2+ from thapsigargin- and inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ pools. In addition, the increase in [Ca2+]i in response to SPC, but not to SP, was attenuated in cells treated with phorbol myristate acetate or with the putative Ca(2+)-channel blocker SKF 96365, and in cells pretreated with pertussis toxin for 24 h. SPC did not activate the production of IP3. Furthermore, both SPC and SP released sequestered Ca2+ from permeabilized cells. We observed that SPC, but not SP, stimulated release of [3H]arachidonate from cells prelabelled with [3H]arachidonate for 24 h. Both SPC and SP stimulated the incorporation of [3H]thymidine into DNA in cells grown in the absence of thyroid-stimulating hormone (TSH). The results suggest that sphingosine derivatives are putative regulators of Ca2+ fluxes in FRTL-5 cells, and that SP and SPC may act on [Ca2+]i via different mechanisms. Furthermore, both SP and SPC may be of importance in modulating thyroid-cell proliferation.

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