Losartan and atenolol on hypertension induced by adenosine receptor blockade

1. The prolonged infusion of 1,3-dipropyl-8-sulfophenylxanthine (DPSPX), a non-selective antagonist of adenosine receptors, induces hypertension, an increase in plasma renin activity and morphological cardiovascular changes. 2. The aim of this work was to evaluate the effects of losartan, a selective AT1 receptor antagonist, and atenolol, a beta-adrenoceptor antagonist, on DPSPX-induced hypertension. 3. Male Wistar rats (250-300 g, n = 4-6) were treated for 1 or 4 weeks with: saline i.p.; DPSPX (90 microg kg(-1) h(-1)) i.p.; losartan (15 mg kg(-1) day(-1)) p.o.; atenolol (25 mg kg(-1) day(-1)) p.o.; DPSPX (90 microg kg(-1) h(-1)) i.p. + losartan (15 mg kg(-1) day(-1)) p.o.; DPSPX (90 microg kg(-1) h(-1)) i.p. + atenolol (25 mg kg(-1) day(-1)) p.o. Blood pressure was measured by the 'tail-cuff' method in conscious animals. Fragments of the mesenteric and tail arteries were processed for morphological study and the mean diameter of the vascular smooth muscle cells was determined. 4. DPSPX increased blood pressure. Losartan and atenolol prevented this rise but had no effect on blood pressure of control rats. DPSPX-treated groups showed hypertrophy of the vascular smooth muscle cells and proliferation of subintimal cells. Losartan but not atenolol prevented these changes. Losartan had no effect on the vascular morphology of control rats, while treatment with atenolol for 4 weeks induced hypertrophy of the vascular smooth muscle cells. 5. Both losartan and atenolol counteract the development of DPSPX-induced hypertension but only losartan prevents the alterations in vascular morphology.     

Serotonin 2A receptor antagonists for treatment of schizophrenia

Introduction: All approved antipsychotic drugs share an affinity for the dopamine 2 (D₂) receptor; however, these drugs only partially ameliorate the symptoms of schizophrenia. It is, therefore, of paramount importance to identify new treatment strategies for schizophrenia.

Areas covered: Preclinical, clinical and post-mortem studies of the serotonin 5-HT_2A system in schizophrenia are reviewed. The implications of a combined D₂ and 5-HT_2A receptor blockade, which is obtained by several current antipsychotic drugs, are discussed, and the rationale for the development of more selective 5-HT_2A receptor antagonists is evaluated. Moreover, the investigational pipeline of major pharmaceutical companies is examined and an Internet search conducted to identify other pharmaceutical companies investigating 5-HT_2A receptor antagonists for the treatment of schizophrenia.

Expert opinion: 5-HT_2A receptor antagonists appear to assume an intermediate position by being marginally superior to placebo but inferior to conventional antipsychotic drugs. Three previous 5-HT_2A receptor antagonists have been discontinued after Phase II or III trials, and available Phase IIa data on the remaining 5-HT_2A receptor antagonist will need substantial additional validation to be approved as a new treatment strategy against schizophrenia.     

Toxicity of cholesterol oxidation products to Caco-2 and HepG2 cells: modulatory effects of alpha- and gamma-tocopherol

Cholesterol can be oxidized to form a variety of cholesterol oxidation products also known as oxysterols. The aims of the present study were to compare the cytotoxic effects of four oxysterols, namely 25-hydroxycholesterol (25-OHC), 7beta-hydroxycholesterol (7beta-OHC), cholesterol-5beta,6beta-epoxide (beta-epox) and cholesterol-5alpha,6alpha-epoxide (alpha-epox), in two human cell culture models. Further, the ability of 10 and 100 micro m alpha- and gamma-tocopherol (alpha-TOC and gamma-TOC, respectively) to protect against oxysterol-induced cytotoxicity was also assessed. Human colonic adenocarcinoma Caco-2 and human hepatoma HepG2 cells were supplemented with increasing concentrations of 25-OHC, 7beta-OHC, beta-epox and alpha-epox (0-25 micro g ml(-1)) for 24, 48 or 96 h. Following 24-h and 48-h exposure, test media were replaced with normal growth media and the cells were maintained for 72 and 48 h, respectively. The 96-h exposure represented a constant challenge to the cells. Cytotoxicity was assessed using the neutral red uptake assay. The concentration of compound that inhibited cell viability by 50% (ic(50) value) was calculated. All four oxysterols investigated induced the greatest cytotoxic effects following 96 h of exposure. 25-Hydroxycholesterol exhibited the greatest cytotoxicity in both cell lines. Both beta-epox and alpha-epox were more toxic to HepG2 cells than to Caco-2 cells after the 48-h exposure. Pretreatment of cells with either alpha- or gamma-TOC did not protect against oxysterol-induced cytotoxicity. The caco-2 cells treated with the high concentration (100 micro m) of gamma-TOC were found to be more susceptible to oxysterol-induced toxicity under the conditions employed in this study.     

5-HT receptor ligands differentially affect operant oral self-administration of ethanol in the rat

The present study evaluated the effects of the selective serotonin (5-hydroxyhyptamine; 5-HT) reuptake inhibitor, fluoxetine, the 5-HT_1B receptor agonist, tetrahydro-4-pyridyl[3,2-b]pyridine, CP-94,253 the preferential 5-HT_2A receptor agonist, 1-(2,5-dimethoxy-4 iodophenyl)-2-aminopropane, DOI and the mixed 5-HT_2C/1B receptor agonist, 1-(3-chlorophenyl)piperazine, mCPP, on oral ethanol (10% v/v) self-administration in a two-lever, fixed-ratio:1, water vs. ethanol choice procedure in the rat. All compounds affected operant behavior, with varying degrees of specificity, that is, the extent to which a reduction of ethanol-reinforced lever pressing coincided with a reduction of ethanol preference, and selectivity, that is, the extent to which a reduction of ethanol-reinforced lever pressing could be dissociated from an effect on total responding on both levers. Fluoxetine (5–20 mg/kg, i.p.) and CP-94,253 (1–10 mg/kg, i.p.) induced a nonselective disruption of operant behavior; the profile being weakly specific for CP-94,253. DOI (0.1–0.3 mg/kg, i.p.) and mCPP (0.3–1 mg/kg, i.p.) induced a specific effect; the profile being more selective for DOI. These findings suggest that operant ethanol self-administration can be suppressed in a specific manner by activation of 5-HT_2A and, possibly, 5-HT_2C receptors, and in a nonselective manner by activation of 5-HT_1B receptors. As fluoxetine indirectly stimulates these receptors and its behavioral profile resembles more that of a 5-HT_1B receptor agonist, activation of 5-HT_1B receptors may underlie its effects on operant ethanol self-administration.     

In vivo pharmacology of irindalone,a 5-HT2 receptor antagonist with predominant peripheral effects

The in vivo effects of irindalone, a newly developed serotonin₂ (5-HT₂) antagonist, have been investigated in comparison with a series of reference compounds. Irindalone potently antagonizes the pressor response induced by 5-HT in pithed rats, but has a 173 times weaker effect against the α₁-adrenoceptor agonist phenylephrine. Irindalone is relatively weak in rat models detecting central 5-HT₂ antagonism, that is, inhibition of quipazine- or I-5-HTP plus citalopram-induced head twitches, inhibition of I-5-HTP plus citalopram-induced increases of flexor reflexes, and inhibition of the discriminative stimulus properties induced by d-LSD. Furthermore, it displaces in vivo ³H-ketanserin binding in frontal cortex. Irindalone weakly antagonizes the flexor reflex stimulated by the α₁-adrenoceptor agonist St 587. No dopamine receptor inhibition is detected in the methylphenidate gnawing test in mice. High bioavailability is indicated by the identical ED₅₀ values obtained in the head twitch model after s.c. and p.o. administration. The activity profile of irindalone resembles that of ketanserin except in two characteristics: ketanserin has greater potency than irindalone as an antagonist in the 5-HTP-induced flexor reflex, but has a shorter duration of action. The effect of irindalone is stereoselective, since its opposite enantiomer Lu 21-099 is almost inactive in the models for central and peripheral 5-HT₂ receptor antagonism. Finally, the effect of repeated treatment with irindalone (18 μmol/kg, p.o., twice daily for 2 weeks) on inhibition of quipazine-induced head twitches was studied. Two days after the last dose, the potency for inhibiting quipazine was unchanged, indicating that no tolerance to 5-HT₂ receptor antagonism develops using this dose regimen. It is concluded that irindalone is a potent 5-HT₂ antagonist with preferential effects at peripheral sites.     

beta-Lactam susceptibility patterns and investigation of cephalosporin hydrolysing beta-lactamases of Gram-negative extraintestinal clinical isolates

Of more than 3500 isolates of enterobacteriaceae, 48–69% were resistant to aminopenicillins and 11–45% to amoxycillin+clavulanic acid. Resistance to second and third generation cephalosporins was present in 11–17 and 3–8% of Escherichia coli, 47–56 and 15–52% of Klebsiella–Enterobacter, 36–57 and 16–27% of Proteus, Providencia and Morganella isolates. Pseudomonas aeruginosa strains varied in their resistance to antipseudomonal β-lactams. Isoelectric points, inhibitor profiles and substrate profiles of β-lactamases extracted from representatives of the resistant strains indicated that the resistance was mainly due to the hyperproduction of chromosomally encoded AmpC β-lactamases. This was confirmed by plasmid profile and PCR investigations. Extended-spectrum β-lactamase and metallo-penicillinase producing strains were not found. One Pseudomonas maltophilia strain produced an oxacillinase.     

Bromocriptine potentiates the behavioural effects of directly and indirectly acting dopamine receptor agonists in mice

Summary After an initial period of depression which lasted up to 90 min following injection, bromocriptine (BRC, 5–20 mg/kg, IP) produced dose-dependent and long lasting (7 h) locomotor stimulation in mice. The locomotor stimulation was antagonised by reserpine, alpha-methyl-p-tyrosine (AMPT) or haloperidol. The blockade by AMPT of BRC's locomotor stimulant effect was reversed by prior treatment of the mice with a low, behaviourally inactive dose of L-Dopa plus benserazide. In mice pretreated with reserpine, BRC enhanced the stimulant action of d-amphetamine. Moreover, in mice pretreated with reserpine plus AMPT, BRC significantly enhanced the locomotor stimulant effect of apomorphine. This ability of BRC to enhance the effect of apomorphine commenced as soon as 20 min after BRC administration and lasted for at least 8 h. The dopamine (DA) uptake inhibitor and DA receptor agonist nomifensine potentiated and prolonged the stimulant effect of BRC while inhibitor of the neuronal uptake of noradrenaline (desipramine) and 5-hydroxytryptamine (fluoxetine) were without marked effect. The results clearly show that BRC, in behavioural terms, has no efficacy per se at the postsynaptic DA receptor and that it requires either DA or the administration of an exogenous agonist such as apomorphine for the expression of its effects.     

A study of anti-inflammatory activity of some novel alpha-amino naphthalene and beta-amino naphthalene derivatives

In the present study, some naphthalene derivatives have been synthesized by incorporating azetidinyl and thiazolidinyl moieties at its alpha- or beta-positions such as alpha-(3-chloro-2-oxo-4-substituted)aryl-1-azetidinyl)naphthalenes 6-10, alpha-((substituted)aryl-4-oxo-1,3-thiazolidin-3-yl)naphthalenes 11-15, beta-(3-chloro-2-oxo-4-substituted aryl-1-azetidinyl)naphthalenes 21-25, and beta-(substituted aryl-4-oxo-1,3-thiazolidin-3-yl)naphthalenes 26-30. These compounds have also been screened for acute toxicity and anti-inflammatory and analgesic activities. Compounds which showed better anti-inflammatory and analgesic activities were also examined for their ulcerogenic liability and underwent a cyclooxygenase assay. Two compounds, 12 and 28, were found to exhibit potent anti-inflammatory activity as compared to the standard drugs phenylbutazone and naproxen.     

The GABA B receptor agonist CGP44532 and the positive modulator GS39783 reverse some behavioural changes related to positive syndromes of psychosis in mice

BACKGROUND AND PURPOSE

An important role of GABAergic neurotransmission in schizophrenia was proposed a long time ago, but there is limited data to support this hypothesis. In the present study we decided to investigate GABA_B receptor ligands in animal models predictive for the antipsychotic activity of drugs. The GABA_B receptor antagonists {"type":"entrez-protein","attrs":{"text":"CGP51176","term_id":"875489595","term_text":"CGP51176"}}CGP51176 and {"type":"entrez-protein","attrs":{"text":"CGP36742","term_id":"877561962","term_text":"CGP36742"}}CGP36742, agonist {"type":"entrez-protein","attrs":{"text":"CGP44532","term_id":"875097404","term_text":"CGP44532"}}CGP44532 and positive allosteric modulator GS39783 were studied.

EXPERIMENTAL APPROACH

The effects of all ligands were investigated in MK-801- and amphetamine-induced hyperactivity tests. The anti-hallucinogenic-like effect of the compounds was screened in the model of head twitches induced by (±)1-(2.5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). Furthermore, the effect of GS39783 and {"type":"entrez-protein","attrs":{"text":"CGP44532","term_id":"875097404","term_text":"CGP44532"}}CGP44532 on DOI-induced frequency of spontaneous excitatory postsynaptic currents (EPSCs) in slices from mouse brain frontal cortices was investigated. The anti-cataleptic properties of the compounds were also assessed.

KEY RESULTS

The GABA_B receptor activators {"type":"entrez-protein","attrs":{"text":"CGP44532","term_id":"875097404","term_text":"CGP44532"}}CGP44532 and GS39783 exhibited antipsychotic-like effects both in the MK-801- and amphetamine-induced hyperactivity tests, as well as in the head-twitch model in mice. Such effects were not observed for the GABA_B receptor antagonists. DOI-induced increased frequency of spontaneous EPSCs was also decreased by the compounds. Moreover, {"type":"entrez-protein","attrs":{"text":"CGP44532","term_id":"875097404","term_text":"CGP44532"}}CGP44532 and GS39783 inhibited haloperidol-induced catalepsy and EPSCs.

CONCLUSION AND IMPLICATIONS

These data suggest that selective GABA_B receptor activators may be useful in the treatment of psychosis.     

Bactericidal activity of oral beta-lactam antibiotics in plasma and urine versus isogenic Escherichia coli strains producing broad- and extended-spectrum beta-lactamases

Bacteria harbouring extended-spectrum β-lactamases (ESBLs), derived by mutation from TEM-1, TEM-2 or SHV-1 β-lactamases, have been described world-wide. The in vitro activities of these enzymes against β-lactam antibiotics, including oral cephalosporins, are well recognised. The aim of this investigation was to assess the bactericidal activity of oral β-lactam antibiotics available in Croatia (amoxicillin/clavulanate, cephalexin, cefuroxime, cefadroxil and ceftibuten), in biological fluids against isogenic Escherichia coli strains producing broad-spectrum (TEM-1, TEM-2 and SHV-1) and extended-spectrum β-lactamases (SHV-2, SHV-3, SHV-4, SHV-5, SHV-12). Bactericidal activity of oral β-lactams in plasma and urine was tested in time-kill experiments and by determining bactericidal titres at different time intervals post-dose. The killing rate of antibiotics in urine was slower than in plasma, but faster than in Mueller–Hinton broth. High bactericidal titres in urine were only maintained throughout the whole dosing interval by ceftibuten against strains producing broad-, SHV-2 and SHV-3 β-lactamases. The older generation cephalosporins can be considered for the therapy of urinary tract infections caused by E. coli harbouring TEM-1, TEM-2 and SHV-1 β-lactamases but a shorter dosing interval is needed. Ceftibuten can be recommended with caution in ESBL producing E. coli except those producing SHV-4, SHV-5 and SHV-12 that confer resistance to it. If these enzymes are produced, fluoroquinolones or carbapenems could be considered.     

Pharmacokinetics and pharmacodynamics of intravenous bumetanide in mutant Nagase analbuminemic rats: importance of globulin binding for the pharmacodynamic effects.

The importance of plasma protein binding of intravenous furosemide in circulating blood for its urinary excretion and hence its diuretic effects in mutant Nagase analbuminemic rats was reported. Based on the furosemide report, the diuretic effects of another loop diuretic, bumetanide, could be expected in analbuminemic rats if plasma protein binding of bumetanide is considerable in the rats. This was proved by this study. After intravenous administration of bumetanide, 10 mg/kg, to analbuminemic rats, the plasma protein binding of bumetanide was 36.8% in the rats mainly due to considerable binding to alpha- and beta-globulins (this value, 36.8%, was considerably greater than only 12% for furosemide), and hence the percentages of intravenous dose of bumetanide excreted in 6 h urine as unchanged drug was 16.0% in the rat (this value was considerably greater than only 7% for furosemide). After intravenous administration of bumetanide to analbuminemic rats, the area under the plasma concentration-time curve from time zero to time infinity (1012 compared with 2472 microg min/mL) was significantly smaller [due to significantly faster both renal clearance (1.49 compared with 0.275 ml/min/kg) and nonrenal clearance (8.30 compared with 3.71 ml/min/kg)], terminal half-life (9.94 compared with 22.4 min) and mean residence time (4.25 compared with 5.90 min) were significantly shorter (due to faster total body clearance, 9.88 compared with 4.05 ml/min/kg), and amount of 6 h urinary excretion of unchanged bumetanide (559 compared with 261 microg, due to increase in intrinsic renal excretion) was significantly greater than that in control rats. The 6 h urine output and 6 h urinary excretions of sodium, chloride and potassium were comparable between two groups of rats although the 6 h urinary excretion of bumetanide was significantly greater in analbuminemic rats. This could be explained by the following. The amount of urinary excretion of bumetanide was significantly greater in analbuminemic rats than that in control rats only between 0 and 30 min urine collection. In both groups of rats, the urinary excretion rates of bumetanide during 0-30 min reached a upper plateau with respect to urine flow rate as well urinary excretion rates of sodium, potassium and chloride, therefore, the diuretic effects (6 h urine output and 6 h urinary excretions of sodium, potassium and chloride) were not significantly different between two groups of rats.     

Study of urinary 6β-hydroxycortisol/cortisol ratio in spot urine sample as a biomarker of 3A4 enzyme activity in healthy and epileptic subjects of Egyptian population

The ratio of urinary 6 beta-hydroxycortisol/cortisol (6 beta-OHC/FC) in morning spot urine samples collected from 8:00 a.m. to 12:00 p.m. was studied using ELIZA kits (Stabiligen) in a group of healthy adult Egyptians (control group) of both sex (n=65, age range: 16-48 years). The frequency distribution of urinary 6 beta-OHC/FC ratio was widely distributed among subjects with higher values in males in comparison to females. No bimodality in either sex was observed. Another group of adult epileptic patients (n=16) was studied for the influence of chronic carbamazepine antiepileptic drug administration on urinary 6 beta-OHC/FC ratio in spot urine samples. The induction property of carbamazepine on CYP3A4 was observed through significant increase (p=0.01) in 6 beta-OHC/FC ratio among epileptic patients in comparison with control subjects. In conclusion, the frequency distribution of urinary 6 beta-OHC/FC ratio among Egyptians shows sexual dimorphism. Also, measurement of urinary 6 beta-OHC/FC ratio provides a simple non-invasive method to monitor CYP3A4 enzyme induction during administration of carbamazepine antiepileptic drug.     

The effect of bromoacetylalprenololmentane on rat atrial tension development and β-adrenoreceptors

In isolated rat atria, 1 μM bromoacetylalprenololmentane shifted the tension development curve for isoproterenol to the right of the control curve. After a 2 h washout period, no significant recovery of the isoproterenol concentration-response curve had occurred. Pretreatment of rat atrial membranes with 1 μM bromoacetylalprenololmentane resulted in an 83% decrease in the concentration of β-adrenoceptors with no change in the K_D value for [¹²⁵I]iodocyanopindolol binding to the receptors left. The results indicated that bromoacetylalprenololmentane was an irreversible β-blocker.     

Estrogenic effects of 17 beta-aminoestrogens assessed in uteri of rats and mice

Administration of exogenous estrogens has been associated with an increase of thromboembolic events. The 17β-aminoestrogens produce anticoagulant effects contrasting with the procoagulant effects of the natural occurring estradiol in rodents. This work compares the estrogenic effects induced by 17β-aminoestrogens prolame, butolame, pentolame, and estradiol in vivo models. Dose–response curves were performed using immature CD1 mice and Wistar rats. The animals were injected with estradiol or 17β-aminoestrogens (0.01 to 1000 μg/kg), or vehicle. The uterine wet and dry weights were determined. The 17β-aminoestrogens increased uterine weight in a dose-dependent manner. The uterotrophic effect produced by estradiol induced lower ED₅₀ (6.5 and 4 μg/kg) and higher E_max values (+523–350%) in mice as compared with those from the rat, indicating more susceptibility of the mice model. The 17β-aminoestrogens are partial estrogenic agonists with a relative uterotrophic effect of estradiol (100%) from 9–86%. Only the ED₅₀ values of 17β-aminoestrogens in CD1 mice showed a direct correlation to the length of the amine group substitution in C-17 since their efficacy and potency were in the order: prolame>butolame>pentolame.     

Blocking effect of serotonin on β-adrenoceptor activity in follicle-enclosed Xenopus oocytes

The effects of serotonin (5-HT) on a β-adrenergic response were studied, using the voltage clamp technique, in Xenopus laevis oocytes surrounded by their follicular cells. noradrenaline induced marked hyperpolarization, with a specific increase in the permeability of the membrane toward K⁺. Application of 10 μM 5-HT had little effect on the resting membrane, but significantly depressed the response to 0.1 μM noradrenaline. The dose-response curve for noradrenaline showed a parallel shift to the right in the presence of 5-HT, suggesting that 5-HT competes with noradrenaline for common binding sites at the β-adrenoceptor.     

The role of beta-lactamase producing bacteria and bacterial interference in streptococcal tonsillitis

The causes of penicillin failure in eradicating group A β-haemolytic streptococcal pharyngo-tonsillitis are described. The mechanisms accounting for the failure include the presence in the tonsils of β-lactamase producing bacteria and the absence of bacterial interference. The use of antimicrobials that can overcome and modulate these two phenomena and achieve better cure of the infection is described.     

Opposite effects of endogenous nitric oxide and prostaglandin F2 alpha in the rat mesenteric bed

1. The relationship between the effects of endogenous nitric oxide (NO) and prostanoids on the noradrenaline (NA)-induced contractions and the mechanisms involved were investigated in the rat perfused mesenteric bed, using NG-nitro-L-arginine methyl ester (l-NAME), a NO synthase inhibitor and sodium nitroprusside (SNP), a NO donor. 2. The constrictor responses to NA were reduced to 50% by the cyclooxygenase inhibitor 10 microm indomethacin as well as by 1 microM SNP. When indomethacin and SNP were perfused simultaneously the contractions were further reduced. 3. The NA-induced contractions were increased by the addition of 400 microM L-NAME and the addition of either indomethacin or SNP abolished such increases. The simultaneous perfusion of both agents further reduced the contractions. 4. Removal of the endothelium increased NA-induced contractions to a similar extent as L-NAME and this increase was abolished by indomethacin as well as by SNP. 5. The perfusion of 10 microM NA augmented the release of prostaglandin (PG) F2 alpha by the mesenteric bed without modifications in any other prostanoid. In the presence of L-NAME, this effect was further increased. However, SNP abolished the NA-induced stimulation of PGF2 alpha release. 6. In de-endothelialized preparations NA also stimulated PGF2 alpha production as observed in intact preparations. This effect was more marked in the presence of L-NAME; in contrast, SNP abolished the stimulation. 7. In conclusion, the present results suggest an opposite action between NO and PGF2 alpha on the NA-induced contractions in the rat mesenteric bed.     

Receptor specificity of the 5HT2 receptor antagonist,LY53857

LY53857 is a potent antagonist at vascular 5HT₂ receptors that lacks prominent α₁ or dopamine antagonist activity. The present report investigates the interaction of LY53857 with other receptor mechanisms. LY53857 showed no agonist activity in the guinea pig trachea, guinea pig atria, guinea pig ileum, or rat vas deferens. Furthermore, LY53857 did not antagonize histamine (H₁) or β₂ receptors in the guinea pig trachea, β₁ in the guinea pig atria, muscarinic, or angiotensin I receptors in the guinea pig ileum. However, LY53857 did block α₂ receptors (?log K_B = 6.51) as determined by antagonism of the inhibitory effects of the selective β₂ agonist, UK-14,304, on the twitch response in the guinea pig ileum. LY53857 antagonized β₂ receptors at concentrations approximately 6000-fold higher than necessary to block 5HT₂ receptors (?log K_B = 10.3). Taken in concert, these data support the contention that LY53857 is a highly selective antagonist of 5HT₂ receptors, and that LY53857 is a useful tool with which to probe 5HT₂ receptors and serotonergic mechanisms.     

Contrasting effects of estradiol and 17 beta-aminoestrogens on blood clotting time in rats and mice

Estrogens have been associated with thromboembolic events. Our group has described the anticoagulant effect of 17β-aminoestrogens in rodents, potentially new alternative estrogenic agents without thrombogenic risk. This work compares the contrasting effects of estradiol and the 17β-aminoestrogens (prolame, butolame, and pentolame) on blood clotting time. Ovariectomized CD1 mice received a single injection of 17β-aminoestrogens, estradiol (20 to 80 mg/kg), or vehicle. Estradiol decreased blood clotting time from −10% to −25% (48 h; P<0.01) and 17β-aminoestrogens increased it, differing in latency (12 h; +48%, P<0.01) and duration (72 h +58%, P<0.01). In male Wistar rats, similar effects (pentolame +45%; estradiol −31%; P<0.01) were observed 48 h after five consecutive daily injections of 1000 μg/animal/day. The maximum procoagulant effect of estradiol was obtained after 72 h with 10 μg/animal/day (−45%; P<0.01). 17β-Aminoestrogens always produced opposite effects to those of estradiol on blood coagulation.     

Effective mast cell degranulating peptide inhibitors of the IgE/Fc epsilonRI receptor interaction

Previous studies with mast cell degranulating (MCD) peptide have shown that peptide [Ala(12)]MCD 8 was an inhibitor of IgE binding to mast cell receptors. In an attempt to produce increased inhibition, analogs were synthesized that maintained the alanine residue in position 12 in the MCD peptide sequence and were further modified at both termini. Analogs modified at the C-terminus were [Ala(12),desLys(21)]MCD 2 and [Ala(12),D-Lys(21)]MCD 4. N-terminus modifications were [desLys(6)-Arg(7)-His(8),Ala(12)]MCD 1, [Ala(6), Ala(12)]MCD 6, and [Val(6),Ala(12)]MCD 7. To assess the role of the Proline(12), analogs [D-Ala(12)]MCD 3 and [Meleu(12)]MCD 5 were also synthesized. The analogs were tested for binding to the IgE receptor in cultured mast cells. Inhibitory activity of IgE-caused degranulation was measured using a beta-hexosaminidase assay. Circular dichroism (CD) and molecular modeling of selected analogs were used to follow possible structural differences among these analogs. All analogs showed binding affinity to the IgE receptor and inhibition of IgE-induced mast cell degranulation at different levels. Differences in inhibition were most likely because of diverse interactions of the analogs with the receptor as inferred by the CD and modeling studies. Based on the results of the beta-hexosaminidase assay, analog [Val(6), Ala(12)]MCD 7 proved to be an excellent inhibitor of IgE-mediated mast cell degranulation.