Ghrelin signaling in human mesenteric arteries.

The hypothesis is that the ghrelin signal pathway consists of new participants including a local second mediator in human mesenteric arteries. The contractile force of isometric artery preparations was measured using a wire-myograph. Whole-cell patch clamp experiments were performed on freshly isolated single smooth muscle cells from the same tissue.

Pancreatic islet overproduction of H2S and suppressed insulin release in Zucker diabetic rats.

Hydrogen sulfide (H(2)S) has been traditionally known for its toxic effects on living organisms. The role of H(2)S in the homeostatic regulation of pancreatic insulin metabolism has been unclear. The present study is aimed at elucidating the effect of endogenously produced H(2)S on pancreatic insulin release and its role in diabetes development.

Ghrelin signalling in guinea-pig femoral artery smooth muscle cells.

Aim: Our aim was to study the new signalling pathway of ghrelin in the guinea-pig femoral artery using the outward I(K) as a sensor.

Methods: Whole-cell patch-clamp experiments were performed on single smooth muscle cells, freshly isolated from the guinea-pig femoral artery. The contractile force of isometric preparations of the same artery was measured using a wire-myograph.

Cocaine- and amphetamine-regulated transcript (CART) peptide as an in vivo regulator of cardiac function in Rana ridibunda frog.

The aim of this study was to investigate the effect of CART peptide on cardiac performance and on the physiological signalling pathways involved using Rana ridibunda frog heart preparations in vivo. The CART peptide, when injected into the venous sinus, significantly and reproducibly increased the force of frog heart contractions by up to 33.0 +/- 6.

Contractile effect of ghrelin on isolated guinea-pig renal arteries.

Ghrelin, a 28-amino acid peptide, known to exist in both acylated and des-acylated varieties, was identified as the first endogenous ligand of growth hormone secretagogue receptor in 1999. Various arteries are known to express ghrelin receptors, but the direct action of ghrelin on blood vessels has been unclear. In the present study we show that ghrelin concentration-dependently potentiates endothelin-1 (ET-1) induced tension development of guinea-pig renal artery, as measured using a wire-type isometric myography of vascular segments.

Ghrelin suppression of potassium currents in smooth muscle cells of human mesenteric artery.

Ghrelin is a 28-amino acid peptide hormone which modulates many physiological functions including cardiovascular homeostasis. Here we report some novel findings about the action of ghrelin on smooth muscle cells (SMC) freshly isolated from human mesenteric arteries. Ghrelin (10(-7) mol/l) significantly suppressed the iberiotoxin-blockable component of potassium currents (I(K)) and depolarized the cell membrane, while having no effect on Ca(2+) currents.

[Urocortin decreases phosphorylation of MYPT1 and increases the myosin phosphatase activity via elevation of the intracellular level of cAMP].

Urocortin, a peptide hormone related to the corticotropin releasing factor, is suggested to be involved in blood pressure regulation by dilating the peripheral blood vessels. In rat tail arteries, urocortin-induced vasodilation is due to a decrease in myofilament Ca2+ sensitivity the mechanism of which is still unclear. In this study, the hypothesis was tested that the decrease in Ca2+ sensitivity in mouse tail arteries results from the activation of myosin light chain phosphatase.

HO-1 induction in the guinea-pig stomach: protection of smooth muscle functional performance during cobalt-induced oxidative stress.

Distribution and enzymatic activity of haem oxygenase (HO) was investigated in the stomach of healthy guinea pigs or animals subjected to in vivo cobalt-induced oxidative stress. The physiological role of HO-1 and HO-2 isoenzymes in fundic and antral area of the stomach was assessed by studying the action of HO substrate--hemin--on ionic currents of single smooth muscle cells. The data obtained suggest that HO-1 induction might serve in the guinea-pig stomach as genetically determined defense mechanism aimed to combat toxic stress-related pathology in order to preserve the functional performance of the organ.

Heme oxygenase-2 products activate IKCa: role of CO and iron in guinea pig portal vein smooth muscle cells.

Hemin (10 microM) and carbon monoxide (CO) increased iberiotoxin-blockable IKCa in portal vein smooth muscle cells. CO-induced IKCa activation was abolished by 10 microM ODQ, 10 microM cyclopiazonic acid and 1 microM KT5823. The hemin-induced effect on IKCa was abolished by pretreatment with Sn-protoporphyrin IX, a heme oxygenase inhibitor and Fe2+ chelator but was insensitive to inhibitors of soluble guanylate cyclase (GC) and cGMP-dependent protein kinase (PKG).

Calcium-dependent changes in potassium currents in guinea-pig coronary artery smooth muscle cells after acute cobalt loading in vivo.

The aim of the present study was to determine whether cobalt poisoning induces haem oxidase isoenzyme-1 (HO-1) in coronary artery smooth muscle, or accounts for any changes in coronary smooth muscle cell (SMCs) membrane ionic currents that could result from this type of heavy metal poisoning. In SMCs isolated from cobalt-treated guinea-pig coronaries, K+ channel currents (IK) were much smaller than those in cells isolated from non-treated animals. Haemin (HO substrate) increased IK concentration dependently.

Hydrogen ions control synaptic vesicle ion channel activity in Torpedo electromotor neurones.

During exocytosis the synaptic vesicle fuses with the surface membrane and undergoes a pH jump. When the synaptic vesicle is inside the presynaptic nerve terminal its internal pH is about 5.5 and after fusion, the inside of the vesicle comes in contact with the extracellular medium with a pH of about 7.

Role of constitutively expressed heme oxygenase-2 in the regulation of guinea pig coronary artery tone.

Carbon monoxide (CO) is well known as a relaxing substance in the vasculature, where it is released during the heme oxygenase (HO) reaction. Little is known about the tissue-specific targets of CO in smooth muscles. To date the functional role of CO in the coronary artery remains unclear.

Effect of cisplatin and cobalt chloride on antioxidant enzymes in the livers of Lewis lung carcinoma-bearing mice: protective role of heme oxygenase.

Changes in the activities of antioxidant enzymes superoxide dismutase, catalase (CAT), glutathione peroxidase and heme oxygenase (HO) and changes in lipid peroxidation and reduced glutathione (GSH) levels were measured in the livers of control and Lewis lung carcinoma (LLC)-bearing mice 24 h after a single injection of cisplatin or CoCl(2). Treatment with cisplatin induced the same degree of lipid peroxidation and GSH depletion as did CoCl(2) but the antioxidant enzymes were differently involved in cisplatin- and cobalt-induced oxidative stress responses. In cobalt-treated mice the activities of these enzymes were either inhibited or not changed significantly and only the HO activity was increased (5-fold) as a main protective enzyme.

Induction of heme oxygenase in guinea-pig stomach: roles in contraction and in single muscle cell ionic currents.

The role of heme oxygenase reaction products in modulation of stomach fundus excitability was studied. The presence of constitutive heme oxygenase 2 was verified in myenteric ganglia by immunohistochemistry. The role of inducible heme oxygenase isoenzyme was investigated after invivo treatment of animals with CoCl2 (80 mg kg-1 b.

Enhanced heme oxygenase activity increases the antioxidant defense capacity of guinea pig liver upon acute cobalt chloride loading: comparison with rat liver.

Changes in the activity of so-called oxidative stress defensive enzymes, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and heme oxygenase, as well as changes in lipid peroxidation and reduced glutathione levels, were measured in guinea pig and rat liver after acute cobalt loading. Cobalt chloride administration produced a much higher degree of lipid peroxidation in guinea pig than in rat liver compared with the control animals. The intrahepatic reduced glutathione content in control guinea pig was higher than that in rat, but was equally decreased in both species after cobalt administration.

Heme oxygenase is the main protective enzyme in rat liver upon 6-day administration of cobalt chloride.

Changes in the activities of rat liver heme oxygenase (HO), superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) and glutathione reductase (GR), as well as changes in lipid peroxidation and reduced glutathione (GSH) levels were measured after acute loading and chronic administration of cobalt chloride (CoCl2). Acute loading was achieved by a single subcutaneous injection of 60 mg CoCl2/kg body weight for 24 h. Chronic administration was performed by giving the same total amount of CoCl2 in small doses over longer periods of time: 30 mg CoCl2/kg daily for 2 days, 15 mg CoCl2/kg daily for 4 days, or 10 mg CoCl2/kg daily for 6 days.

Urocortin relaxes rat tail arteries by a PKA-mediated reduction of the sensitivity of the contractile apparatus for calcium.

1. Urocortin is an endogenous vasodilator although the mechanism of vasorelaxation is not completely understood. The hypothesis that an alteration of smooth muscle calcium concentration is involved was tested using isometric tension recording and calcium fluorimetry.

Thyrotropin-releasing hormone activates KCa channels in gastric smooth muscle cells via intracellular Ca2+ release.

Thyrotropin-releasing hormone (TRH) is released in high concentrations into gastric juice, but its direct effect on gastric smooth muscles has not been studied yet. We undertook studies on TRH effect on gastric smooth muscle using contraction and patch clamp methods. TRH was found to inhibit both acetylcholine- and BaCl2-induced contractions of gastric strips.

Urocortin hyperpolarizes stomach smooth muscle via activation of Ca2+-sensitive K+ currents.

The effect of urocortin (Uro), a recently discovered neuropeptide with selectivity towards corticotropin-releasing hormone type 2 receptor, was tested on whole cell currents expressed by guinea-pig gastric antrum smooth muscle cells. Uro (1 pmol/l-1 nmol/l) caused a concentration-dependent increase of Ca2+-sensitive K currents (I(K)) up to 500% as compared to control currents and did not affect the kinetics and voltage-dependence of inward Ca2+ currents. The I(K)-increasing effect of Uro was fully antagonized by preliminary emptying of intracellular Ca2+ stores with ryanodine and cyclopiazonic acid, as well as by bath application of selective blockers of adenylyl cyclase and cAMP-dependent protein kinase (PKA), but not by inhibitors of guanylyl cyclase, cGMP-dependent protein kinase, and protein kinase C.

4-aminopyridine affects rat arterial smooth muscle BK(Ca) currents by changing intracellular pH.

The hypothesis whether or not 4-AP can affect vascular smooth muscle BK(Ca) currents was tested using the patch-clamp technique, pH- and calcium-fluorimetry, and freshly isolated rat arterial smooth muscle cells. Application of 4-AP reversibly inhibited BK(Ca) currents at an intracellular calcium ([Ca](i)) of 250 nM with a half-block of 2. 5 mM at +50 mV.

Corticotropin-releasing hormone acts on guinea pig ileal smooth muscle via protein kinase A.

In contraction studies corticotropin-releasing hormone (CRH) was found to relax ileal but not gastric and jejunal smooth muscles of the guinea-pig, precontracted with BaCl2. Under whole-cell patch-clamp conditions, CRH concentration-dependently activated Ca2+-sensitive K+ currents (IK) with ED50=20 pM at 100 nM and ED50=0. 13 pM at 500 nM intracellular Ca2+ respectively.

Multitude of ion channels in the regulation of transmitter release.

The presynaptic nerve terminal is of key importance in communication in the nervous system. Its primary role is to release transmitter quanta on the arrival of an appropriate stimulus. The structural basis of these transmitter quanta are the synaptic vesicles that fuse with the surface membrane of the nerve terminal, to release their content of neurotransmitter molecules and other vesicular components.

Two populations of smooth muscle cells in the guinea-pig gastric antrum.

K+ outward currents (I[K]) expressed by guinea-pig antral smooth muscle cells were studied using the whole-cell voltage-clamp technique. In about 88% of cells depolarization steps applied from Vh = -70 mV activated a fast transient component (I[K(to)]) with voltage-dependent characteristics, and a noninactivating component with slow activation kinetics (I[K(sl)]). Both components were carried by K+ ions.

Oxytocin-induced changes in single cell K+ currents and smooth muscle contraction of guinea-pig gastric antrum.

To study the effects of oxytocin on both spontaneous phasic contractions and K+ outward currents (IK) of the so-called 'non-target' smooth muscle cells, physiological concentrations of oxytocin ranging between 10(-12) mol/l and 10(-8) mol/l were applied to smooth muscle preparations and single voltage-clamped cells isolated from the circular layer of the guinea-pig gastric antrum. Oxytocin (10(-12) mol/l to 10(-8) mol/l) suppressed, in a dose-dependent manner, the tetrodotoxin- and atropine-resistant spontaneous phasic contractions and shifted rightward the dose-response curves of 10(-7) mol/l charybdotoxin and 10(-3) mol/l BaCl2. In cells with preloaded intracellular Ca2+ stores, oxytocin (10(-12) mol/l to 10(-9) mol/l) caused a dose-dependent activation of the charybdotoxin-blockable non-inactivating component of IK (IK(sl)) of single voltage-clamped cells, which was accompanied by hyperpolarization of the cell membranes.

Two components of potassium outward current in smooth muscle cells from the circular layer of human jejunum.

Two components of the outward K+ currents (Ik) of cells isolated from the circular layer of human jejunum were investigated using the conventional whole-cell voltage clamp method. A fast transient Ik component could only be elicited by depolarization in cells dialysed with pipette solution of pCa < 7.4.