bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of hypoxia and metabolic inhibitors on production of prostacyclin and endothelium‐derived relaxing factor by pig aortic endothelial cells
Authors: Richards Joanna M. , Gibson Ian F. , Martin William 
Published: July 2012

The content of adenosine triphosphate (ATP) and basal and bradykinin‐stimulated production of prostacyclin and endothelium‐derived relaxing factor (EDRF) was measured in primary cultures of porcine aortic endothelial cells under normoxic (14.4% O2) and hypoxic (2.8% O2) conditions, and following treatment with rotenone and 2‐deoxy glucose, which inhibit oxidative and glycolytic metabolism, respectively.
ATP content and basal and bradykinin‐stimulated production of prostacyclin were similar under normoxic and hypoxic conditions. EDRF production, assessed as endothelial guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) content, was also similar under both conditions.
Treatment with rotenone (0.3 μm) had no effect on ATP content or basal or bradykinin‐stimulated production of prostacyclin or of EDRF, measured as endothelial cyclic GMP content. Elevation of cyclic GMP content by atriopeptin II was also unaffected.
Treatment with 2‐deoxy glucose (20 mm) in glucose‐free Krebs solution lowered ATP content, reduced bradykinin‐stimulated production of prostacyclin and abolished the bradykinin‐stimulated elevation of cyclic GMP content. Resting production of prostacyclin was unaffected but basal content of cyclic GMP was lowered in some experiments. Elevation of cyclic GMP content by atriopeptin II was abolished.
Combined treatment with rotenone (0.3 μm) and 2‐deoxy glucose (20 mm) lowered ATP content more than with 2‐deoxy glucose alone. Basal production of prostacyclin rose slightly and bradykinin‐stimulated production was powerfully inhibited. Basal content of cyclic GMP was unaffected, but bradykinin‐stimulated production was abolished. Elevation of cyclic GMP by atriopeptin II was also abolished.
Cascade bioassay experiments using endothelium‐denuded rings of rabbit aorta as a detector system confirmed that bradykinin‐stimulated production of EDRF was blocked by 2‐deoxy glucose, but not by rotenone.
These data indicate that porcine aortic endothelial cells in culture operate under mainly glycolytic metabolism and this probably explains why production of prostacyclin and EDRF is unaffected under hypoxic conditions. They also indicate that glycolytic metabolism is required for agonist‐stimulated production of prostacyclin and EDRF by these cells.
Modulation of the hypothermic and hyperglycaemic effects of 8‐OH‐DPAT by α2‐adrenoceptor antagonists
Authors: Durcan Michael J. , Wozniak Krystyna M. , Linnoila Markku 
Published: July 2012

The effects of pretreatment with two novel and relatively specific α2‐adrenoceptor antagonists on the hypothermic and hyperglycaemic responses induced by the 5‐HT1A receptor agonist 8‐hydroxy‐2‐(di‐n‐propylamino)tetralin (8‐OH‐DPAT) were investigated in mice. The α2‐adrenoceptor antagonists used were, atipamezole, which occupies both central and peripheral receptors, and L 659,066, which poorly penetrates the blood brain barrier.
Atipamezole (1 and 3 mg kg−1) alone had no effect on body temperature but significantly attenuated the 8‐OH‐DPAT‐induced hypothermic response. The hyperglycaemic effect of 8‐OH‐DPAT was also attenuated by pretreatment with atipamezole; however, 3 mg kg−1 atipamezole did cause some hypoglycaemia when administered alone.
Pretreatment with L 659,066 (3–30 mg kg−1) failed to alter the hypothermic effects of 8‐OH‐DPAT. All doses of L 659,066 tested attenuated 8‐OH‐DPAT‐induced hyperglycaemia, but the highest dose (30 mg kg−1) produced hypoglycaemia when administered alone.
The results suggest that the attenuation of 8‐OH‐DPAT‐induced hypothermia by α2‐adrenoceptor antagonists may be centrally mediated whereas the blockade of 8‐OH‐DPAT‐induced hyperglycaemia may involve peripheral mechanisms.
Stimulation of neutrophil adherence to vascular endothelial cells by histamine and thrombin and its inhibition by PAF antagonists and dexamethasone
Authors: Watanabe Masako , Yagi Mikio , Omata Mitsugu , Hirasawa Noriyasu , Mue Suetsugu , Tsurufuji Susumu , Ohuchi Kazuo 
Published: July 2012

In order to clarify the roles of platelet‐activating factor (PAF) in histamine‐ and thrombin‐induced neutrophil adhesion to vascular endothelial cells, the effects of several PAF antagonists were examined. The effects of the glucocorticoid dexamethasone were also examined in order to gain further insight into the anti‐inflammatory actions of glucocorticoids.
In culture, histamine and thrombin stimulated the adherence of rat peritoneal neutrophils to human endothelial cells from the umbilical vein. They did not stimulate neutrophil adherence in the absence of endothelial cells, suggesting that the target cells for the histamine‐ and thrombin‐induced adherence of neutrophils were endothelial cells, not neutrophils.
Several PAF antagonists, such as CV‐3988, L‐652,731 and Y‐24,180 inhibited the histamine‐ and thrombin‐induced neutrophil adherence in a concentration‐dependent manner. Indomethacin failed to inhibit it.
Dexamethasone, a steroidal anti‐inflammatory drug, did not inhibit the histamine‐ and thrombin‐induced adherence of neutrophils to endothelial cells when the drug was present only during the 20 min incubation period for the adherence assay. When the endothelial cells were preincubated for 3 h with dexamethasone, the adherence of neutrophils to endothelial cells induced by histamine or thrombin was not inhibited.
When the neutrophils were preincubated for 3 h with dexamethasone, the histamine‐ and thrombin‐induced adherence of neutrophils to endothelial cells was inhibited.
Our studies indicate that: (a) adherence of neutrophils to endothelial cells induced by histamine and thrombin is mediated by PAF production since PAF antagonists inhibited the adherence of neutrophils; and (b) neutrophils, not endothelial cells, are the target cells through which dexamethasone acts to inhibit adherence.
Parainfluenza virus infection damages inhibitory M2 muscarinic receptors on pulmonary parasympathetic nerves in the guinea‐pig
Authors: Fryer Allison D. , Jacoby David B. 
Published: July 2012

The effect of viral infection on the function of neuronal M2 muscarinic autoreceptors in the lungs was studied in anaesthetized guinea‐pigs.
Guinea‐pigs were inoculated intranasally with either parainfluenza type 3 or with a vehicle control. Four days later the animals were anaesthetized, paralysed and artificially ventilated. Pulmonary inflation pressure, tidal volume, blood pressure, and heart rate were recorded. Both vagus nerves were cut and electrical stimulation of the distal portions caused bronchoconstriction (measured as an increase in pulmonary inflation pressure) and bradycardia.
In control animals, pilocarpine (1–100 μg kg−1, i.v.) attenuated vagally‐induced bronchoconstriction by stimulating inhibitory M2 muscarinic receptors on parasympathetic nerves in the lungs. Conversely, blockade of these receptors with the antagonist gallamine (0.1–10 mg kg−1, i.v.) produced a marked potentiation of vagally‐induced bronchoconstriction. These results confirm previous findings.
In guinea‐pigs infected with parainfluenza virus, pilocarpine did not inhibit vagally‐induced bronchoconstriction. Furthermore, gallamine did not potentiate vagally‐induced bronchoconstriction to the same degree as in uninfected controls.
There was no increase in baseline pulmonary inflation pressure in the infected animals over the controls. Receptors on airway smooth muscle were unchanged by viral infection since large doses of pilocarpine caused equivalent bronchoconstriction in both groups of animals. Gallamine inhibited the vagally‐induced fall in heart rate equally in both groups of animals indicating that virus‐induced changes in M2 receptor function on pulmonary parasympathetic nerves are not part of a generalized decrease in M2 receptor function.
These results demonstrate that the M2 muscarinic receptor‐mediated inhibition of acetylcholine release from parasympathetic nerves in the lungs is decreased in animals infected with parainfluenza virus. Loss of this inhibition would result in increased release of acetylcholine from the parasympathetic nerves and may explain virus‐induced airway hyperresponsiveness.
Changes in brain striatum dopamine and acetylcholine receptors induced by chronic CDP‐choline treatment of aging mice
Authors: Giménez Rosa , Raïch Josep , Aguilar Juan 
Published: July 2012

Spiroperidol binding (dopamine D2 receptors) and quinuclidinyl benzilate binding (muscarinic receptors) in striata of 19‐month old mice was analyzed for animals that had received chronic administration of cytidine 5′‐diphosphocholine (CDP‐choline) incorporated into the chow consumed (100 or 500 mg kg−1 added per day) for the 7 months before they were killed.
Treated animals displayed an increase in the dopamine receptor densities of 11% for those receiving 100 mg kg−1 and 18% for those receiving 500 mg kg−1 as compared to the control aged animals that had received no CDP‐choline. Control animals showed, from 2 months to 19 months of life, a 28% decrease in the receptor density. No change in the affinity of the receptors for spiroperidol was found in the treated or untreated animals.
Muscarinic acetylcholine receptor densities were also partially recovered by the same treatment in aged animals that showed a 14% decrease of these receptors in this case. The muscarinic receptor density increased 6% for the animals that received 100 mg kg−1 and 17% for the animals that received 500 mg kg−1 without any change in the affinity of the receptor for quinuclidinyl benzilate.
Aged animals displayed a slight increase in brain membrane fluidity as indicated by a decrease in the polarization value of the non‐polar fluorophore 1,6‐diphenyl‐1,3,5‐hexatriene. Interestingly, in the treated animals a greater increase in membrane fluidity was determined and found to be very similar for the two doses.
It is concluded that chronic administration of CDP‐choline to aged animals promoted a partial recovery of the striatum dopamine and acetylcholine receptor function normally reduced with aging, which might be explicable in terms of mechanisms involving fluidity of the brain neuronal membrane.
Delineation of three pharmacological subtypes of α2‐adrenoceptor in the rat kidney
Authors: Uhlén Staffan , Wikberg Jarl E.S. 
Published: July 2012

Simultaneous computer modelling of plain and ARC 239‐ and guanoxabenz‐masked [3H]‐RX821002 saturation curves, plain ARC 239 and guanoxabenz competition curves as well as ARC 239‐masked guanoxabenz competition curves revealed that the drugs bound to three α2‐adrenoceptor subtypes in the rat kidney with grossly differing selectivities. These α2‐adrenoceptor subtypes were termed α2A, α2B1 and α2B2. The order of affinities for [3H]‐RX821002 for the adrenoceptor sites was α2A > α2B1 > α2B2, the Kd s being 0.62 ± 0.05, 2.52 ± 0.11 and 6.74 ± 1.21 nm, respectively. The order of affinities for ARC 239 was α2B1 > α2B2 ≫ α2A with Kd s 4.78 ± 1.04, 28.8 ± 4.1 and 1460 ± 270 nm, respectively. For guanoxabenz the order of affinities was α2A > α2B1 ≫ α2B2 with Kd s 99.7 ± 15.1, 508 ± 135 and 25,400 ± 2400 nm, respectively.
Binding constants for 14 compounds for the three rat kidney α2‐adrenoceptor subtypes were determined by the simultaneous computer modelling of plain and ARC 239‐ and guanoxabenz‐masked drug competition curves, plain ARC 239 and guanoxabenz competition curves as well as ARC 239‐masked guanoxabenz competition curves. Of the 14 compounds tested, oxymetazoline and guanfacine were found to bind with low affinities to both of the α2B1‐ and α2B2‐adrenoceptors but with high affinity to the α2A‐adrenoceptor. Prazosin instead bound with high affinities to the α2B1‐ and α2B2‐adrenoceptors but with low affinity to the α2A‐adrenoceptor. By contrast, guanoxabenz and ARC 239 delineated clearly between all the three α2‐adrenoceptor subtypes. Notably the affinities of guanoxabenz for α2B1‐ and α2B2‐adrenoceptors differed 72 fold and for α2A‐ and α2B2‐adrenoceptors 380 fold. The selectivities of a number of other drugs were less marked but their Kd s were consistent with all three sites being α2‐adrenoceptors.
(−)‐Adrenaline and (−)‐noradrenaline showed dissimilar order of affinities for the three α2‐adrenoceptors. For (−)‐adrenaline the order of affinities was α2B1 ≥ α2A > α2B2 and for (−)‐noradrenaline α2B2 ≥ α2B1 > α2A. All three α2‐adrenoceptors showed the expected stereoselective binding for adrenaline enantiomers, the (+)‐form being 7–10 fold less potent than the (−)‐form.
[3H]‐yohimbine was also used as radioligand. The data with this ligand were fully compatible with the [3H]‐RX821002 data. However, [3H]‐yohimbine appeared to label only α2B1‐ and α2B2‐adrenoceptors presumably because it had too low an affinity for α2A‐adrenoceptors.
We conclude that three pharmacological subtypes of α2‐adrenoceptors are labelled by [3H]‐RX821002 in the rat kidney. Guanoxabenz and ARC 239 may be used in competition studies to delineate between these three α2‐adrenoceptor subtypes. Moreoever, we here present a method allowing the determination of binding constants for an arbitrary drug to the three α2‐adrenoceptor subtypes.
The control of the contraction of myocytes from guinea‐pig heart by the resting membrane potential
Authors: Mermi J. , Yajima M. , Ebner F. 
Published: July 2012

The influence of different holding potentials (− 120 to − 70 mV) on the contraction of enzymatically dispersed myocytes from guinea‐pig hearts was evaluated. Contractions were elicited by repetitive depolarizations to 0 mV at 0.5 Hz.
While ineffective at 140 and 5 mmol 1−1 [Na+]o and pipette Na+, respectively, depolarization of the resting membrane with the holding potential increased myocyte shortening at reduced Na+ gradients ([Na+]o 70 or [Na+]i 10–15 mmol 1−1). Elevated intracellular Na+ after Na+‐pump inhibition with ouabain 1–10 μmol 1−1 was similarly effective with regard to the inotropic response to different holding potentials.
At − 70 mV holding potential, reduction of [Na+]o from 140 to 70 mmol 1−1 increased myocyte shortening and induced an inwardly directed component of the holding current which peaked at − 44 ± 10 pA and declined thereafter in parallel with the inotropic effect. The relation of this inward current to [Ca2+]i was confirmed by experiments at high Ca2+ buffer capacity where [Na+]o reduction induced a Ni2+‐insensitive, outwardly directed component (36 ± 15 pA) of the holding current. The observed inward current is suggested to reflect the extrusion of [Ca2+]i in exchange for [Na+]o as a counter‐regulatory mechanism which limits the increase of [Ca2+]i.
The interventions which increased the strength of the contraction also enhanced the transient tail current after repolarization, suggesting its close relation to [Ca2+]i. This finding confirmed the pattern found with cell shortening.
It is concluded that under certain conditions, voltage‐dependent and Na+‐dependent Na+‐Ca2+ exchange during the interval between the contractions is relevant to the diastolic concentration of [Ca2+]i which in turn determines the accumulation of Ca2+ in the sarcoplasmic reticulum and the magnitude of the subsequent contraction.
A calcitonin gene‐related peptide (CGRP) antagonist (CGRP8–37) inhibits microvascular responses induced by CGRP and capsaicin in skin
Authors: Hughes S.R. , Brain S.D. 
Published: July 2012

The effect of the calcitonin gene‐related peptide (CGRP) antagonist CGRP8–37 on responses to CGRP and other mediators was investigated in rabbit dorsal skin.
Blood flow changes at intradermally‐injected sites were measured by a multiple site 133xenon clearance technique. CGRP8–37 had little effect on blood flow at doses up to 0.3 nmol/site, when injected alone, although a significant increase in blood flow was observed at the highest dose tested (1 nmol/site).
CGRP8–37 dose‐dependently inhibited the increased blood flow induced by human αCGRP and human βCGRP, but had no effect on equivalent vasodilator responses induced by vasoactive intestinal peptide (VIP) and prostaglandin E1 (PGE1). CGRP8–37 showed a preferential ability to inhibit αCGRP (IC50 0.04 nmol), when compared with βCGKP (IC50 ≥ 0.3 nmol).
Capsaicin, which selectively activates sensory nerves, caused a dose‐dependent increase in blood flow when injected intradermally into rabbit skin. The effects of capsaicin (0.01–0.1 μmol/site) were inhibited by CGRP8–37 (0.3 nmol/site), with a partial but significant attenuation of blood flow induced by the highest dose of capsaicin.
Oedema formation, induced by intradermal histamine injection (3 nmol/site), was measured in rabbit skin by the local accumulation of intravenously‐injected 125I‐labelled albumin. Vasodilator doses of CGRP, PGE1 and capsaicin potentiated, in a synergistic manner, oedema formation induced by histamine. CGRP8–37 totally inhibited the potentiating effect of CGRP, partially inhibited the synergistic effect of capsaicin, but did not affect PGE1‐induced responses.
The results suggest that capsaicin acts to release a rabbit form of CGRP in skin and that CGRP8–37 is a useful antagonist for investigating the potential of CGRP as a neurogenic mediator of inflammation.
The effect of inhibitors of nitric oxide biosynthesis and cyclic GMP formation on nerve‐evoked relaxation of human cavernosal smooth muscle
Authors: Pickard R.S. , Powell P.H. , Zar M.A. 
Published: July 2012

The inhibitory transmission in isolated preparations of cavernosal smooth muscle from human penis has been studied.
Electrical field stimulation (EFS; 2–64 pulses/train, 0.8 ms pulse duration, 10 Hz) evoked relaxation of preparations treated with guanethidine (50 μm). The EFS‐evoked relaxations were atropine‐resistant and tetrodotoxin‐sensitive indicating their origin to be non‐adrenergic, non‐cholinergic (NANC) nerve stimulation.
EFS‐evoked relaxation was attenuated dose‐dependently by the nitric oxide (NO)‐synthase inhibitor, l‐NG‐nitro arginine (l‐NOARG; 0.3–100 μm) but not by d‐NG‐nitro arginine. The inhibitory effect of l‐NOARG on transmission was antagonized by l‐arginine (100 μm), a NO precursor, but not by d‐arginine.
Incubation with methylene blue (10–50 μm), a known inhibitor of guanylate cyclase activation by NO, caused a concentration‐related inhibition of EFS‐evoked relaxation.
It is concluded that NANC nerve‐evoked relaxation of human cavernosal smooth muscle is mediated by NO or a NO‐like substance.
Effects of the glycine prodrug milacemide (2‐N‐pentylaminoacetamide) on catecholamine secretion from isolated adrenal medulla chromaffin cells
Authors: Yadid Gal , Zinder Oren , Youdim Moussa B.H. 
Published: July 2012

Milacemide (2‐n‐pentylaminoacetamide) is a glycine prodrug which readily crosses the blood brain barrier and increases brain glycine and glycineamide. In vitro and in vivo studies, with numerous tissues, including adrenal chromaffin cells, have clearly shown that the formation of the latter metabolites is exclusively mediated by monoamine oxidase B for which milacemide is a substrate.
Milacemide, glycineamide and glycine caused a time‐ and dose‐dependent release of catecholamines from bovine isolated chromaffin cells.
Milacemide (10−4 m) induced catecholamine release was roughly 30% of that initiated by acetylcholine (10−4 m), the natural secretagogue.
The combined effects of milacemide (10−4 m) and acetylcholine (10−4 m) on catecholamine secretion from chromaffin cells is additive, suggesting that milacemide does not act through the normal nicotinic receptor release mechanism.
The release of catecholamines from chromaffin cells in response to milacemide (10−4 m) was partially inhibited by the selective MAO‐B inhibitors (−)‐deprenyl (10−7 m) and AGN 1135 (10−6 m). This indicates that the MAO‐B derived metabolites, glycineamide and glycine, contribute to the secretion of catecholamines as does milacemide itself.
It is apparent that release of catecholamines by glycine is mediated by its uptake into the cells since [3H]‐glycine uptake and catecholamine release showed a higly significant correlation (r = 0.96).
Beneficial effect of beraprost, a prostacyclin‐mimetic agent, on post‐hypoxic recovery of cardiac function and metabolism in rabbit isolated hearts
Authors: Tanonaka Kouchi , Maruyama Youichi , Takeo Satoshi 
Published: July 2012

The present study was undertaken to determine whether beraprost, a stable prostacyclin‐mimetic agent, may exert a beneficial effect on post‐hypoxic recovery of cardiac function and metabolism. Isolated rabbit hearts were perfused by the Langendorff method for 20 min under glucose‐free hypoxic conditions, followed by 45 min reoxygenation in the presence of glucose, and their functional and metabolic changes with or without beraprost‐treatment were examined.
Hypoxic insult induced cessation of cardiac contractile force, depletion of myocardial high‐energy phosphates, accumulation of tissue calcium, and release of creatine kinase and ATP metabolites. Subsequent reoxygenation resulted in a poor recovery of cardiac contractile force (less than 10% of the pre‐hypoxic value), a poor restoration of high‐energy phosphates, and increase in calcium content. A further release of creatine kinase and ATP metabolites from the heart was observed during reoxygenation.
Treatment with 0.45 μm beraprost during the whole hypoxic period resulted in a significant suppression of the increase in tissue calcium, and the release of creatine kinase and ATP metabolites during hypoxic perfusion. This treatment also elicited a significant post‐hypoxic recovery of the cardiac contractile force and the tissue high‐energy phosphates. Reoxygenation‐induced release of creatine kinase and ATP metabolites was also prevented by treatment with beraprost.
When hearts were treated with prostacyclin sodium (0.50 μm) in the same manner for the purpose of comparison, similar improvement of post‐hypoxic contractile and metabolic recovery were observed.
These results demonstrate that treatment with either beraprost or prostacyclin is beneficial for post‐hypoxic recovery of cardiac function and metabolism. Since the observed effects on post‐hypoxic contractile recovery were exerted at a concentration of approximately 0.50 μm of these agents (a concentration far from the physiological range) the underlying mechanism appears to be different from the physiological action of prostacyclin.
Effects of selective D1 and D2 dopamine agonists on cockroach salivary gland acinar cells in vitro
Authors: Evans A.M. , Green K.L. 
Published: July 2012

The ability of the selective dopamine receptor agonists, fenoldopam and SKF38393 (D1) and quinpirole and LY163502 (D2), to mimic the effect of dopamine on cockroach salivary gland acinar cells has been investigated.
Intracellular recordings of the membrane potential established that all the agonists mimicked dopamine (i.e. they induced a hyperpolarization which was occasionally followed by a depolarization), whether applied by addition to the superfusate or locally by pressure ejection.
The rank order of potency of the agonists to induce a hyperpolarization was (equipotent molar ratio relative to dopamine in parentheses): dopamine (1) ≫ fenoldopam (1000) > SKF38393 (3500) > LY163502 (13750) > quinpirole (35000).
The agonists also elicited secretion from the salivary gland when superfused onto the preparation. SKF38393 and quinpirole did not induce the same maximum rate of secretion as dopamine. The rank order of potency of the agonists was (minimum effective concentration in parentheses): dopamine (0.03 μm) > fenoldopam (4.8 μm) > SKF38393 (40.8 μm) > quinpirole (132 μm).
Both the hyperpolarizing and secretory responses to all the agonists were antagonized by the selective D1 antagonist, (+)‐SCH23390, but not the selective D2 antagonist, (±)‐sulpiride.
These results support the idea that the same receptors mediate both the hyperpolarizing and secretory responses, and that they are similar to the mammalian D1 receptor.