bluuebunny/crossref_metadata_2025_split huggingface dataset:
The pharmacological evaluation of LY170680, a novel leukotriene D4 and E4 antagonist in the guinea‐pig
Authors: Boot J.R. , Bond A. , Gooderham R. , O'Brien A. , Parsons M. , Thomas K.H. 
Published: July 2012

This paper describes the evaluation of LY170680 (5‐<3‐[2(R) (carboxyethylthio)‐1(S)‐hydroxypentadeca 3(E)5(Z)‐dienyl]phenyl > 1H tetrazole, as an antagonist of the cysteinyl leukotrienes C4, D4, E4, in a variety of in vitro and in vivo models.
In vitro, LY170680 was a potent, selective, and competitive antagonist of LTD4, and LTE4. It produced a concentration‐dependent rightward displacement of the concentration‐response curves elicited by either LTD4 or LTE4 on both the guinea‐pig ileal and tracheal preparation. The pA2 values for LY170680 were estimated to be 8.1 ± 0.2 (n = 8) and 8.1 ± 0.1 (n = 6) on trachea, and 8.7 ± 0.1 (n = 12) and 9.0 ± 0.3 (n = 6) on ileum for both LTD4 and LTE4 respectively. The slopes of the Schild plots in these studies were all close to unity.
LY170680 was shown to be a modest antagonist of the LTC4‐induced responses on guinea‐pig ileum (pA2 7.0 ± 0.2 n = 5), but had no discernable effects against contractions induced by histamine, prostaglandin E2 (PGE2), PGF2α or acetylcholine. The compound also reduced the LTC4‐induced responses on trachea, but in a non competitive manner.
Intravenous LY170680 reduced in a dose‐dependent manner (ED50 3.8 mg kg−1, 60 min pretreatment) the fall in compliance in the anaesthetized guinea‐pig, and the rise in total pulmonary resistance (TPR) (ED50 2.0 mg kg−1, 30min pretreatment) in the artificially ventilated guinea‐pig, produced by intraveous LTD4.
LY170680 (5 mg kg−1, i.v.) was also effective in reducing the increase in TPR to intravenous antigen in sensitized animals pretreated with mepyramine, indomethacin and propranolol.
The compound was only moderately effective (ED50 40 mg kg−1 p.o.) in preventing the rise in TPR induced by intravenous LTD4, when given orally.
Inhaled LY170680 was particularly effective in preventing the increase in TPR produced by an exposure to aerosolised LTD4. An estimated 1–2 μg of LY170680 delivered to the airways by nebuliser 1 hour beforehand, produced a 6 fold lateral displacement to the right of the dose‐response curve to LTD4.
Studies in conscious animals indicated that inhaled LY170680 produced a dose‐dependent reduction in the increased volume of gas, trapped in the lung following exposure to aerosolised LTD4. Duration studies also indicated that an estimated inhaled dose of 10 μg LY170680 significantly reduced the LTD4‐induced increase in trapped lung gas volume for at least 4 h. Inhaled LY170680 also reduced LTC4‐induced increase in gas trapping in a manner similar to LTD4. However, histamine‐induced gas trapping was unaffected.
Vasodilator responses to dopamine in rat perfused mesentery are age‐dependent
Authors: Wanstall Janet C. , O'Donnell Stella R. 
Published: July 2012

Dose‐dependent vasodilator responses to dopamine, isoprenaline, noradrenaline, 3‐isobutyl‐1‐methylxanthine (IBMX) and sodium nitroprusside were obtained in isolated perfused mesentery preparations, taken from reserpine‐treated rats of different ages. The preparations were pretreated with phenoxybenzamine (1 μm) and perfused with physiological salt solution containing cocaine (10 μm), additional KCl (20 mM) and vasopressin (0.1 μm).
Vasodilator responses to dopamine were abolished by the dopamine1 (DA1)‐selective antagonist SCH 23390 (10 nM) and those to isoprenaline by propranolol (1 μm), but the vasodilator responses to noradrenaline were abolished only when SCH 23390 and propranolol were used together. This indicated that dopamine was acting via DA1‐receptors, isoprenaline via β‐adrenoceptors and that noradrenaline could act via DA1‐receptors and β‐adrenoceptors in this preparation.
Responses to all the vasodilator drugs decreased in magnitude between the ages of 1 and 2 months. Responses to dopamine declined further in 4 month‐old rats and were negligible at 6 or 22–24 months of age. Responses to isoprenaline were well maintained up to 6 months of age, but were negligible at 22–24 months.
It is concluded that, in the rat mesenteric vasculature, there is a non‐specific decline in responses to vasodilator drugs during development (1 to 2 months). Subsequently there is a specific decline in DA1‐receptor‐mediated and β‐adrenoceptor‐mediated responses; the former are lost at an earlier age than the latter. This different time course suggests that age influences receptor numbers, or their coupling to adenylate cyclase, rather than a post‐receptor event in the adenylate cyclase/cyclic AMP pathway.
Functional and binding studies with muscarinic M2‐subtype selective antagonists
Authors: Lazareno S. , Roberts F.F. 
Published: July 2012

The potency of a series of selective muscarinic antagonists has been measured on two functional isolated tissue preparations (rat ileum and atria) and these compared with their potency on a range of binding preparations in order to determine whether the subtypes of M2 receptor measured functionally are the same as those measured in binding studies.
On the functional preparations pirenzepine, hexahydrosiladiphenidol (HSD) and 4‐diphenylacetoxy‐N‐methylpiperidine (4‐DAMP) were more potent on the ileum than on the atrium (3 fold, 29 fold and 5 fold respectively), whereas himbacine, AF‐DX 116 and methoctramine showed the opposite selectivity (5 fold, 3 fold and 56 fold respectively). Atropine had a similar potency on the ileum and atrium.
[3H]‐N‐methyl scopolamine was used to study M2 binding sites on membranes from rat heart and rat submandibular gland. Each preparation appeared to contain a homogeneous binding site population. The potencies of the five M2 selective antagonists (and pirenzepine) in binding studies to heart membranes were very similar to those observed in functional studies of rat atria (correlation coefficient = 0.98). Similarly the binding to submandibular gland membranes was very similar to that observed in functional studies on rat ileum (correlation coefficient = 0.97).
[3H]‐pirenzepine was used to examine the binding of these antagonists to M1 binding sites on membranes from rat cerebral cortex. The affinities of 4‐DAMP, HSD, AF‐DX116 and himbacine at M1 sites were similar to their affinities on the gland. Only pirenzepine and methoctramine had higher affinity on M1 sites than on the gland.
Himbacine had a 20 fold lower affinity at M1 binding sites than at heart sites, and it should therefore be an important tool in identifying M1 sites.
Inhibition of [3H]‐N‐methyl scopolamine binding to rat ileum and rat brainstem by M2‐selective antagonists was best described by a two‐site model. In both cases the major population of sites (70–90%) appeared to be similar to sites found on the heart (correlation coefficients = 0.95 and 0.97). The other site appeared to be similar to that on the submandibular gland (correlation coefficients = 0.96 and 1.00).
The correlations observed in these studies in which a range of selective muscarinic antagonists was used lend weight to previous studies indicating the presence of three functionally important muscarinic receptor subtypes, typified by the binding sites studied in the cerebral cortex, submandibular gland and heart.
We propose that the sub‐classification of the M2 muscarinic receptor into M2 and M3 subtypes on the basis of ligand binding studies should be extended to cover functionally‐defined receptors as well.
NK1‐receptors mediate the proliferative response of human fibroblasts to tachykinins
Authors: Ziche Marina , Morbidelli Lucia , Pacini Marco , Dolara Piero , Maggi Carlo Alberto 
Published: July 2012

The effect of synthetic tachykinin selective receptor agonists was studied on the growth of cultured human skin fibroblasts (HF).
Human fibroblasts were grown in serum‐free conditions in the presence of natural tachykinins (substance P and neurokinin A) and of three synthetic agonists, [β‐Ala4, Sar9, Met(O2)11]‐SP(4–11), [β‐Ala8]‐NKA(4–10) and [MePhe7]‐NKB selective for NK1‐, NK2‐ and NK3‐receptors respectively. Cell proliferation was measured by percentage increase in cell number and by [3H]‐thymidine uptake following 48 h exposure to agents compared to baseline condition.
Neurokinin A (NKA) and substance P (SP) significantly increased cell proliferation the threshold concentrations being 10−12 and 10−11 m, respectively. Addition of thiorphan to culture conditions enhanced the effect of SP but not of NKA.
The selective NK1‐receptor agonist produced a dose‐dependent increase in cell proliferation as judged by total cell number and [3H]‐thymidine uptake. No significant effect was observed with NK2‐ and NK3‐receptor agonists.
These data indicate that the effect of SP on fibroblast proliferation is mediated by interaction with a NK1‐receptor type and local metabolism can interfere with the full expression of this effect of SP on cell proliferation.
Inhibitory effects of MK‐886 on arachidonic acid metabolism in human phagocytes
Authors: Ménard Luc , Pilote Sylvie , Naccache Paul H. , Laviolette Michel , Borgeat Pierre 
Published: July 2012

We have investigated the inhibitory activity of compound MK‐886 (formerly L‐663,536), an indole derivative, on 5‐lipoxygenase product synthesis in various human phagocytes stimulated with either the ionophore A23187, in the presence and absence of exogenous arachidonic acid, or platelet‐activating factor (PAF). The lipoxygenase products were analysed by reversed‐phase h.p.l.c.
MK‐886 inhibited the formation of 5‐hydroxy‐eicosatetraenoic acid (5‐HETE), leukotriene B4 (LTB4), its ω‐oxidation products and 6‐trans‐isomers with an IC50 value of 10–14 nm in A23187‐stimulated neutrophils. In the same system, nordihydroguaiaretic acid (NDGA), AA‐861 and L‐655,240 showed IC50 values of 250–510, 110–420 nm and 1.7–3.9 μm, respectively.
MK‐886 inhibited 5‐lipoxygenase product synthesis in A23187‐stimulated blood eosinophils and monocytes, and in neutrophils primed with granulocyte‐macrophage colony‐stimulating factor and stimulated with PAF with IC50 values of 1–13 nm.
The inhibitory activity of MK‐886 was not reversed by addition of 10 μm arachidonic acid to A23187‐stimulated neutrophils.
Compound MK‐886 had no effect on 15‐lipoxygenase product synthesis in blood eosinophils and neutrophils up to a concentration of 1 μm.
At 100 nm compound MK‐886 had no significant effects on calcium ion mobilization, superoxide anion production and actin polymerization in neutrophils.
In conclusion, MK‐886 is a very potent and specific inhibitor of both LTB4 and LTC4 synthesis in various types of human phagocytes.
Electrophysiological and mechanical effects of calcitonin gene‐related peptide on guinea‐pig atria
Authors: Ohmura Tsuyoshi , Nishio Matomo , Kigoshi Shigeru , Muramatsu Ikunobu 
Published: July 2012

The effects of calcitonin gene‐related peptide (CGRP) on mechanical and electrophysiological responses were studied in the guinea‐pig atrial muscle preparations and in single cells.
CGRP (>10−9m) enhanced the twitch contraction in a concentration‐dependent manner in electrically driven left atria and increased heart rate in spontaneously beating right atria. The positive inotropic and chronotropic effects of CGRP were not inhibited by propranolol but were attenuated by reduction of the calcium concentration in the bathing medium.
In single left atrial cells, CGRP slightly hyperpolarized the resting potential but did not affect the other action potential parameters significantly.
Under whole‐cell voltage‐clamp conditions, CGRP increased the calcium inward current. The peptide also increased the steady inward current elicited by hyperpolarization and the late outward current by depolarization.
These results suggest that CGRP may produce the positive inotropic and presumably chronotropic effects by increasing calcium inward current. CGRP also increases the potassium permeability. Such effects on ionic currents may not produce any apparent change in the action potential conformation, due to their opposite directional actions and relatively weak potencies.
Reactivity and sensitivity of mesenteric vascular beds and aortic rings of spontaneously hypertensive rats to endothelin: effects of calcium entry blockers
Authors: Criscione L. , Nellis P. , Riniker B. , Thomann H. , Burdet R. 
Published: July 2012

The vasoconstrictor effects of endothelin‐1 were studied in perfused mesenteric vascular beds (MVB) and aortic rings of 14–16 week‐old spontaneously hypertensive rats (SHR) and age‐matched Wistar Kyoto rats (WKY).
Reactivity to endothelin‐1 was increased in MVBs of SHR, as indicated by the maximum perfusion pressure obtained (264 ± 8 and 141 ± 9 mmHg respectively) (P < 0.001), whereas sensitivity was not significantly different between the two strains (EC50 171 ± 21 and 102 ± 19, respectively).
In aortic rings, in constrast, reactivity to endothelin‐1 was reduced in SHR as compared to WKY, whereas sensitivity was similar (EC50 0.78 ± 0.08 and 0.87 ± 0.09 nm).
As with endothelin‐1, reactivity to noradrenaline and potassium chloride was increased in MVBs, but not in aortic rings of SHR. Endothelin‐1 was 30 times more potent than noradrenaline in MVBs of SHR, and 15 times more potent than noradrenaline in aortic rings.
In both strains, nifedipine and nitrendipine almost completely blocked potassium‐induced contractions in MVB and aortic rings, respectively, whereas contractions induced by endothelin‐1 or noradrenaline were only partially inhibited.
It is concluded that calcium influx via the voltage‐operated calcium channel is only partially responsible for the vasoconstrictor action of endothelin‐1 in MVBs and aortic rings of SHR and WKY rats. The increased reactivity of the MVB of SHR to endothelin‐1 at this stage of the hypertensive process is most likely to be the result of a change in vascular structure rather than due to a primary hypertensive mechanism.
Inositol phospholipid hydrolysis in human brain; adenosine inhibition of the response to histamine
Authors: Kendall D.A. , Firth J.L. 
Published: July 2012

Inositol phospholipid hydrolysis was examined in human cerebral cortex slices by a [3H]‐inositol prelabelling assay.
Enhancement of [3H]‐inositol phosphates accumulation was observed in the presence of carbachol, noradrenaline, histamine, 5‐hydroxytryptamine (5‐HT) and depolarizing concentrations of KCl.
Despite having no effect alone, adenosine (and its analogue 2‐chloroadenosine) selectively inhibited the direct response to histamine.
The inhibition due to adenosine was antagonized by theophylline, but not by 8‐cyclopropyltheophylline.
Actions of second messengers synthesized by various spasmogenic agents and their relation to mechanical responses in dog tracheal smooth muscle
Authors: Katsuyama Hideaki , Suzuki Satoshi , Nishiye Eiichiro 
Published: July 2012

The effects of the spasmogenic agents, carbachol (CCh), histamine, 5‐hydroxytryptamine (5‐HT) and 9,11‐epithio‐11,12‐methano‐thromboxane A2 (STA2) were investigated on smooth muscle tissues of the dog trachea.
CCh (10 μm) produced a larger contraction than high K (128 mm), 10 μm histamine, 5‐HT or STA2. Histamine and 5‐HT produced the same amplitude of contraction as each other. In Ca‐free solution containing 0.2 mm EGTA, only a phasic contraction was evoked by the above agents (except for K which induced no contraction at all).
In skinned muscle tissues, the maximum amplitude of contraction that could be induced by Ca (10 μm) was slightly larger than the maximum CCh‐induced contraction (also at 10 μm) evoked in intact muscle tissues. Caffeine and inositol 1,4,5‐trisphosphate(IP3) both produced contraction.
CCh, histamine and 5‐HT (10 μm) produced a sustained contraction for over 30 min and also increased phosphorylation of the 20 kD protein of myosin light chain (MLC20) for over 30 min with no attenuation. Greater concentrations of the above agents caused more phosphorylation of MLC20.
CCh (above 1 nm), histamine (above 10 nm) and 5‐HT (above 100 nm) increased the amount of IP3, in a concentration‐dependent manner. Synthesis of IP3 induced by the above agents reached its peak value within 30 s and lasted for about 3 min. The potencies for the synthesis of IP3 were in the following order: CCh > histamine > 5‐HT > STA2.
Isoprenaline (10 μm) markedly enhanced but CCh (10 μm) slightly reduced the amount of cyclic AMP. 5‐HT (10 μm) and STA2 (10 μm) reduced, but histamine (10 μm) and CCh (10 μm) increased the amount of cyclic GMP.
Using fura 2, cytosolic Ca was measured by monitoring the ratio of the fluorescent signal excited at 340 and 380 nm wavelengths in the presence of extracellular Ca. CCh (10 μm) increased the Ca transient from 182 nm to 1.42 μm. When the CCh‐induced peak Ca transient (10 μm) was normalised, 10 μm histamine, 5‐HT and STA2 showed smaller values such as 0.49, 0.53 and 0.04 times the control, respectively, and these values corresponded well with the amplitudes of contraction evoked by each of the stimulants.
The results can be summarized as follows: stronger spasmogenic responses occur on application of CCh than on application of 5‐HT or histamine, and STA2 may have a minor role as a spasmogenic agent. The maximum amplitudes (peaks) of contraction evoked by the above spasmogenic agents are closely related to the maximum increase in cytosolic Ca, but sustained contraction and increased phosphorylation of myosin cannot be explained by the increased amount of Ca. In the case of 5‐HT and histamine, synthesized cyclic nucleotides may interact with the action of IP3 for the regulation of contraction in a positive or negative manner, respectively.
P2‐, but not P1‐purinoceptors mediate formation of 1,4,5‐inositol trisphosphate and its metabolites via a pertussis toxin‐insensitive pathway in the rat renal cortex
Authors: Nanoff Christian , Freissmuth Michael , Tuisl Elisabeth , Schütz Wolfgang 
Published: July 2012

The adenosine receptor (P1‐purinoceptor) agonists N6‐cyclopentyladenosine and N‐5′‐ethyl‐carboxamidoadenosine at concentrations up to 10 μmol l−1 affected neither basal, nor noradrenaline‐ and angiotensin II‐stimulated formation of inositol‐1‐phosphate, inositol‐1,4‐bisphosphate, and inositol‐1,4,5‐trisphosphate in slices of rat renal cortex.
In contrast, adenine nucleotides (P2‐purinoceptor agonists) markedly stimulated inositol phosphate formation. The observed rank order of potency adenosine‐5′‐O‐(2‐thiodiphosphate) (EC50 39 μmol l−1) > adenosine‐5′‐O‐(3‐thio triphosphate) (587) ≥ 5′‐adenylylimidodiphosphate (App(NH)p, 899) > adenylyl‐(β,γ‐methylene)‐diphosphonate (4,181) was consistent with the interaction of the compounds with the P2y‐subtype of P2‐purinoceptors. AMP and the ADP analogue (α,β‐methylene)‐adenosine‐5′‐diphosphate were ineffective. ATP and ADP (≤ 10 mmol l−1) did not produce a consistent increase, owing to their hydrolytic degradation in the incubation medium.
Whereas the inositol phosphate response to App(NH)p was linear only up to 5 min incubation, the time‐dependent stimulation of noradrenaline declined at a slower rate. Following pre‐exposure of the renal cortical slices to App(NH)p, renewed addition of App(NH)p caused no further enhancement in the accumulation of inositol phosphates, whilst noradrenaline was still capable of eliciting a response. This suggests that the apparent loss of responsiveness to App(NH)p is not due to substrate depletion or enzymatic inactivation, but most likely attributable to homologous desensitization of the purinoceptor.
Pretreatment of the animals with pertussis toxin caused a substantial reduction of functional Gi‐protein, as indicated by the lack of [32P]‐NAD incorporation in a membrane preparation of the renal cortex. Nevertheless, the increase in inositol phosphate formation induced by noradrenaline, angiotensin II, and App(NH)p was not significantly impaired.
We conclude that P2y‐purinoceptors are present in the renal cortex; these receptors stimulate formation of inositol phosphates via a pertussis toxin‐insensitive pathway and undergo homologous desensitization. On the other hand, our results suggest that renal A1‐adenosine receptors do not use stimulation of phosphoinositide breakdown as a transmembrane signalling system.
Preferential biliary elimination of FPL 63547, a novel inhibitor of angiotensin‐converting enzyme, in the rat
Authors: Carr R.D. , Cooper A.E. , Hutchinsno R. , Mann J. , O'Connor S.E. , Robinson D.H. , Wells E. 
Published: July 2012

The route of elimination of FPL 63547, a novel inhibitor of angiotensin‐converting enzyme (ACE), has been investigated in the anaesthetized rat. Comparisons have been made with other ACE inhibitors.
Bile and urine samples were collected over a 5 hour period following a single i.v. dose of ACE inhibitor (2 μmol kg−1). Samples were bioassayed for ACE inhibitory activity using affinity‐purified rabbit lung ACE and the amounts of the active form of inhibitor present in each sample were calculated by comparison with a standard curve.
FPL 63547 was rapidly and extensively excreted as the diacid in the bile but appeared in the urine in negligible amounts. The bile:urine ratio was 21.4:1 indicating a marked preference for the biliary route. A similar elimination profile was observed when the compound was dosed in its active form (FPL 63547 diacid), 87.9% of which was found in the bile over the 5 h collection period, with a bile: urine ratio of 14.6:1.
The marked preference of FPL 63547 for biliary elimination was not shared by the other ACE inhibitors tested in this study. Lisinopril demonstrated the opposite pattern, being excreted almost exclusively by the kidney (bile:urine ratio 0.06:1). Enalapril was eliminated in approximately equal amounts in bile and urine (ratio 0.7:1) while spirapril diacid showed a slight preference for the bile (ratio 2.6:1).
The physical chemical properties of FPL 63547 diacid may be responsible for its unusual preference for biliary elimination. In particular, the amphipathic character and strong acid functionality of the compound are thought to favour transport into the bile.
Elimination by the biliary route will be preferred in patients whose renal function is impaired as a result of disease or age. In such patients the elimination of renally‐excreted ACE inhibitors is known to be compromised, resulting in compound accumulation and the need for closer monitoring. Therefore, the elimination profile of FPL 63547, if confirmed in man, may prove to be clinically advantageous.
Cardiovascular responses to verapamil and nifedipine in hypoventilated and hyperventilated rats
Authors: Achike Francis I. , Dai Soter 
Published: July 2012

The influence of hypoventilation or hyperventilation on blood pressure and pulse rate responses to verapamil and nifedipine was studied in chloralose‐anaesthetized rats.
Artificial ventilation with room air at a fixed volume of 10 ml kg−1 successfully induced combinations of hypoxaemia, hypercarbia and acidosis at a ventilator rate of 37 strokes min−1 and of hyperoxaemia, hypocarbia and alkalosis at 160 strokes min−1.
Hypoventilation caused significant decreases in both the blood pressure and pulse rate, whereas hyperventilation produced significant increases in these parameters.
In the controls, intravenous injections of graded doses of either verapamil or nifedipine caused dose‐dependent decreases in mean blood pressure. The effects on pulse rate were not marked.
The hypotensive effects of verapamil were significantly more intense in hyperventilated rats, whereas those of nifedipine were significantly less pronounced in hypoventilated animals. The hypoventilated rats exhibited a significant dose‐dependent decrease in pulse rate in response to verapamil administration.
It is concluded that cardiovascular responses to verapamil, nifedipine and probably other calcium antagonists are altered in the presence of blood gas abnormalities.