Pulmonary and hemodynamic effects of histamine in the pig. In vitro and in vivo studies

The purpose of this study was: (1) to investigate the distribution of H₁- and H₂- histaminergic receptors in the pulmonary artery and vein of the pig, and (2) to observe the hemodynamic and respiratory effects induced by 10 min of i.v. infusion of histamine in the anesthetized pig. D-chlorpheniramine and cimetidine were used as H₁- and H₂-receptor antagonists. Our results demonstrate a contractile response of the isolated pulmonary vein and artery (i.d. from 2.0 to 2.5 mm) which is mediated by H₁-receptors. The i.v. infusion of histamine was followed by an early significant increase of heart rate (HR) and mean pulmonary artery pressure. Subsequently a significant fall of cardiac output (CO) and dynamic pulmonary compliance were observed in association with hypoxia and hemoconcentration. After d-chlorpheniramine the infusion of histamine induced a marked pulmonary and systemic vasodilatation, hypotension and an increase in HR and CO. These effects could be dependent on a direct stimulation of H₂-receptors possibly present in the smallest pulmonary vessels. Most of the effects observed during the infusion of histamine alone persisted after cimetidine administration. Moreover an increase of the pulmonary dynamic compliance was observed during H₁-receptor stimulation. The combined blockade of H₁- and H₂-receptors prevented all the described effects.     

Radiographic contrast media-induced histamine release: a comparative study with mast cells from different species

Radiographic contrast media in clinical use cause unwanted allergic and pseudoallergic reactions. To investigate the mechanisms of these reactions, studies on isolated mast cells from different species and sites are necessary. In this study, the effect of six commonly used contrast media on rat (peritoneal, lung) and human (lung) mast cells was investigated. The three preparations with low osmolalities (Hexabrix, Solutrast, Ultravist) released little or no histamine from the cells examined. In contrast, the three preparations with high osmolalities (Angiographin, Telebrix, Rayvist) were potent releasing agents. However, the degree of release and the order of potency was different depending on the cells investigated. Indeed, rat peritoneal mast cells required much higher concentrations before release was observed. Since the contrast media with low osmolality also cause histamine release and reactions in vivo, other systems (e.g. complement) must be additionally involved.     

Biotransformation of nonionic X-Ray contrast agents In vivo and In vitro.

Liposomes loaded with the nonionic iodinated contrast agent iodixanol were injected i.v. into monkeys, rats, and dogs, and liver samples were analyzed by HPLC and mass spectrometry. Two metabolites (M1 and M2), with UV spectra identical to those of the iodixanol isomers (exo and endo) and with a mass increase of 162 compared with iodixanol, were detected. Incubations of iodixanol-liposomes or iodixanol in rat liver homogenates resulted in large amounts of iodixanol metabolites, whereas no metabolites were formed in other organ or tissue homogenates. Four groups of unidentified HPLC peaks were detected: M1 and M2 with a relative retention similar to the metabolite peaks of the in vivo samples, and in addition the minor M3 and M4. UV spectrum analysis indicated that M1 and M3 were structurally related to the iodixanol exo-isomer, whereas M2 and M4 were related to the endo-isomer. Mass spectrometry techniques indicated that the metabolites were conjugates containing one or two hexose residues, which by carbohydrate analysis and experiments with concanavalin A-Sepharose and alpha- and beta-glucosidase were shown to be glucose residues bound to iodixanol through O-alpha1-glycoside-like linkages. Metabolites with similar mass increments also were detected for several other nonionic contrast agents after in vitro incubations in liver homogenates. In conclusion, M1 and M3 are conjugates of the iodixanol exo-isomer with one and two glucose adducts, respectively. M2 and M4 are similar conjugates of the iodixanol endo-isomer. This is the first report on hepatic biotransformation of this class of X-ray contrast agents.     

In vivo studies on histamine catabolism and its inhibition

1. Histamine catabolism in vivo was studied in mice subjected to various forms of pretreatment; tissues from mice killed 2.5 min after intravenous injection of (14)C-histamine were assayed for (14)C-histamine, (14)C-methylhistamine and total (14)C.2. Pretreatment of mice with aminoguanidine, an inhibitor of diamine oxidase, strongly increased levels of (14)C-histamine in intestine; pretreatment with aminoguanidine plus a monoamine oxidase inhibitor strongly increased levels of (14)C-methylhistamine in liver. Effects in other tissues are reported and discussed.3. Pretreatment of mice with non-isotopic methylhistamine increased levels of (14)C-histamine in liver. Methylhistamine is the first known inhibitor of histamine-methylation in vivo.4. Pretreatment of mice with inhibitors of protein synthesis, drugs which reduce the basal activity of histidine decarboxylase and which block its activation, failed to affect histamine catabolism.5. Pretreatment of mice with endotoxin or with Freund's adjuvant, irritants known to cause activation of histidine decarboxylase, failed to affect histamine catabolism.6. There was no evidence of parallelism between the histamine-destroying enzymes and the histamine-forming enzyme, histidine decarboxylase, either in distribution or ability to undergo changes in activity. No support was obtained for the view that histamine-catabolizing enzymes play a role in the local control of responses to newly formed histamine.     

Controlled release of huperzine A from biodegradable microspheres: In vitro and in vivo studies

This paper describes the effect on Sun Protection Factor (SPF) of the combination of inorganic and organic filters in sunscreen products as determined by an in vitro method. O/W emulsions containing inorganic filters, such as titanium dioxide and zinc oxide, combined with 18 EU-authorized UV-B organic filters were tested. SPF measurements were carried out using a spectrophotometer equipped with an integrating sphere.

This study observed a synergic effect when titanium dioxide was combined with either anisotriazine or octyldimethylPABA. The combination of zinc oxide with 11 UV-B organic filters also exhibited a similar synergy; however, the measured SPF was systematically lower than the protection factor achieved with titanium dioxide.     

A quaternary ammonium glucuronide is the major metabolite of lamotrigine in guinea pigs. In vitro and in vivo studies.

Urinary excretion of a variety of quaternary ammonium glucuronides has been generally reported to be confined to humans and some monkeys. Lower animal species appear to lack or have limited ability to form these unusual metabolites. In this report, the excretion of the quaternary ammonium glucuronide of lamotrigine, an investigational 1,2,4-triazine anticonvulsant, in guinea pigs is described. Lamotrigine 2-N-glucuronide accounted for 60% of an i.v. bolus dose of lamotrigine in guinea pig urine. Less than 6% of the dose was excreted unchanged. The pharmacokinetics of lamotrigine after an iv bolus dose of 10 mg/kg were determined with an ion-pairing, reversed-phase HPLC assay. Lamotrigine is a low clearance drug (Cl = 2.51 +/- 0.063 ml/min/kg) with a large volume of distribution (Vss = 2.23 +/- 0.403 liter/kg). The half-life of lamotrigine was 11.5 +/- 2.0 hr. The elimination of the glucuronide was formation rate-limited and it was excreted by extensive tubular secretion. The glucuronide was also formed in Triton-X-100-activated liver microsomes and isolated guinea pig hepatocytes. The KM was 2.10 +/- 0.44 mM and the Vmax was 0.252 +/- 0.0312 nmol/min/mg protein in untreated microsomes. Pretreatment with beta-naphthoflavone did not induce lamotrigine glucuronidation. In hepatocytes, production of the glucuronide was linear for 60 min after a short lag period and 2 mM lamotrigine was not cytotoxic. Lamotrigine is only the second example of a compound that is primarily metabolized to a quaternary ammonium glucuronide in a lower animal species.     

In vitro inhibition of allergic histamine release by calcium antagonists

The ability of calcium entry blockers to inhibit allergic histamine release from rabbit leukocytes was studied. Bepridil, verapamil, nifedipine, diltiazem and TMB-8 produced concentration-dependent inhibition of allergic histamine release from rabbit leukocytes. The calculated IC50s (microM) were as follows: verapamil = 1.3; bepridil = 2.3; TMB-8 = 3.0; nifedipine = 3.3; and diltiazem = 5.3. Verapamil also exerted concentration-dependent inhibition of allergic histamine release from human basophils with an IC50 of 3.7 microM. These agents may act by interfering with the influx of Ca2+ into the leukocytes as well as calcium-dependent steps (e.g., activation of calmodulin, phospholipase A2 and/or 5-lipoxygenase etc.) in the process of histamine secretion.     

利培酮微球在家兔体内外的释药行为

目的制备生物可降解的利培酮微球,并考察其在家兔体内外的释放。方法以聚乳酸羟基乙酸为基质,乳化-溶剂挥发法制备利培酮微球,并进行长期及加速体外释放和家兔体内释放研究。结果体外释药可采用溶蚀-扩散模型拟合,微球体内释药平稳,体内外释放相关性好。结论利培酮在体内外具有缓释效果,可采用加速释放实验来模拟体内外释放。     

In vitro and in vivo studies on the metabolism of tirofiban.

Tirofiban hydrochloride [L-tyrosine-N-(butylsulfonyl)-O-[4-(4-piperidinebutyl)] monohydrochloride, is a potent and specific fibrinogen receptor antagonist. Radiolabeled tirofiban was synthesized with either (3)H-label incorporated into the phenyl ring of the tyrosinyl residue or (14)C-label in the butane sulfonyl moiety. Neither human liver microsomes nor liver slices metabolized [(14)C]tirofiban. However, male rat liver microsomes converted a limited amount of the substrate to a more polar metabolite (I) and a relatively less polar metabolite (II). The formation of I was sex dependent and resulted from an O-dealkylation reaction catalyzed by CYP3A2. Metabolite II was identified as a 2-piperidone analog of tirofiban. There was no evidence for Phase II biotransformation of tirofiban by microsomes fortified with uridine-5'-diphospho-alpha-D-glucuronic acid. After a 1 mg/kg i.v. dose of [(14)C]tirofiban, recoveries of radioactivity in rat urine and bile were 23 and 73%, respectively. Metabolite I and unchanged tirofiban represented 70 and 30% of the urinary radioactivity, respectively. Tirofiban represented >90% of the biliary radioactivity. At least three minor biliary metabolites represented the remainder of the radioactivity. One of them was identified as I. Another was identified as II. When dogs received 1 mg/kg i.v. of [(3)H]tirofiban, most of the radioactivity was recovered in the feces as unchanged tirofiban. The plasma half-life of tirofiban was short in both rats and dogs, and tirofiban was not concentrated in tissues other than those of the vasculature and excretory organs.     

A modified radioimmunoassay for the detection of histamine release in vivo and in vitro in man.

Histamine (Hi) release in vitro or in vivo in man was measured by variants of a radioimmunoassay (RIA) procedure. Hi released from isolated basophils was converted enzymically to N-tau-methylhistamine (NMH) which was then measured by a very sensitive RIA. This modified RIA was compared with the standard spectrofluorometric assay and was found to have additional advantages in certain applications. RIA of NMH in plasma was found to be of value in acute medical conditions of obscure aetiology.     

Metabolism of sulfadiazine in neonatal and young pigs. Comparative in vivo and in vitro studies

Metabolism of sulfadiazine (SDZ) was studied in vivo and in vitro during postnatal development of piglets in order to examine whether in vitro metabolism approaches the in vivo situation. Experiments were performed in 1-day-, 8-day- and 60-day-old piglets. In vivo: 14C-SDZ was injected intravenously and urine and tissue samples collected after 3 hr. Urinary excretion data as well as data from liver and kidney tissue indicated a relatively high capacity for acetylation at birth, while the capacity for oxidation is low during the first week of life. At 60 days of age the acetylation and oxidation of SDZ is equal each accounting for about 20% of the amount excreted in urine. In vitro: Incubation of subcellular fractions of liver and kidney showed that acetylation of SDZ in liver reached maximum within 1 week. Oxidative activity was absent at 1 day, present at a low level at day 8, and at a high level at day 60. Neither acetylation nor oxidation of SDZ took place in kidney. The results show a close correlation between in vivo and in vitro results with respect to the developmental pattern seen in piglets during the postnatal period of life.     

头孢呋辛-聚甲基丙烯酸甲酯珠链的体内外释放

头孢呋辛－聚甲基丙烯酸甲酯珠链的体内,外释放过程。方法测定Ｃｅｆ对骨水泥聚合热的稳定性,制成５％和２．５％,Ｃｅｆ－ＰＭＭＡ珠链,观察其体内、外释放过程。结果Ｃｅｆ经过加热１００℃１ｈ后是稳定,完全可以耐受骨水泥聚合絷;５％和２．５％Ｃｅｆ－ＰＭＭＡ珠链的体外翻动释过程为ｄ１、２释放速度最快,最量大,然后明显下降,缓慢释放达３００ｄ,２．５％球链的缓释效果优于５％珠链;体内释放过程与体外相似,但最     

In vivo and in vitro release of cyanide from neurotoxic aminonitriles

Cyanide release from neurotoxic aminonitriles was measured following in vitro incubation with both microsomes and liver slices. Investigation of cyanide released as urinary thiocyanate following ip aminonitrile administration to rats was also measured. The yield of cyanide in the in vivo study, as measured by the mole percent of administered dose, was greatest from dimethylaminonitrile (DMAA), followed by trimethylaminopropionitrile (TMAPN), dimethylaminopropionitrile (DMAPN), 3,3'-iminodipropionitrile (IDPN), dimethylaminobutyronitrile (DMABN), and monomethylaminopropionitrile (MMAPN). Urinary excretion of thiocyanate accounted for 48.9% of the administered DMAA, 11.6% of TMAPN, 8.0% of DMAPN, 6.8% of IDPN, 3.1% of DMABN, and 1.8% of MMAPN. Incubation of aminonitriles and related compounds with microsomes or liver slices from rats yielded measurable quantities of cyanide from all the compounds tested except for DMABN, TMABN, and succiononitrile. Quantitative evaluation of the yield of formaldehyde by demethylation following microsomal incubation was also determined. The signs of acute toxicity in rats after ip administration of KCN were similar only to those in rats administered DMAA.     

In vitro and in vivo safety studies of a proprietary whey extract.

A proprietary whey growth factor extract (WGFE) or Lactermin (Lact milk; ermin growth factors) is a whey fraction of milk containing the major proteins lactoperoxidase and lactoferrin, together with a variety of minor proteins and peptides such as the growth factors IGF-I, IGF-II, PDGF, FGF, TGF-ss and betacellulin. This growth factor component of milk has been suggested to possess biological properties such as the promotion of tissue repair and anti-inflammatory activity. In this study the safety of Lactermin has been evaluated using genotoxicity assays (Ames, mouse lymphoma and micronucleus assay) and in a subchronic (13 week) rat oral toxicity study. In vitro Lactermin did not show any mutagenic properties in the Ames or mouse lymphoma assay and in vivo did not show any adverse clinical effects or in the bone marrow of male or female mice. In the subchronic oral toxicity study in which 10 rats per sex were fed Lactermin mixed with rat diet to deliver doses of 300, 1000 and 3000 mg/kg/day for 13 weeks, male and female rats did not show any test article-related clinical observations or effects on body weight, food consumption, ophthalmic effects, functional observational battery, organ weights, locomotor activity, hematology, serum chemistry, urinalysis or macroscopic or microscopic pathology. The results from the genotoxicity studies and the subchronic oral toxicity study suggest Lactermin is safe for consumption with a no-observed-adverse-effect level (NOAEL) of 3000 mg/kg/day.     

In vitro and in vivo studies on chelation of manganese

This work deals with new chelating agents of manganese (Mn). Out of 24 compounds chosen for their chemical structure supposed to be favorable for Mn complexation, six polyaminopolycarboxylic acids proved to be efficient for displacing Mn bound to serum bovine proteins in vitro: TTHA, DTPA, DPTA, DPTA-OH, HBED, EDTA (mobilization > or =50%). The first five compounds were then tested in vivo on rats pretreated with MnCl2. They exhibited only slight to moderate efficacy to diminish Mn in tissues and were ineffective on increased Mn concentration in whole blood; in addition, they had different and specific mobilizing effects on other essential elements (Fe, Zn, Cu). Their limited efficacy in vivo could be due to the formation of very stable complexes between Mn2+ and different molecules such as hemoglobin and certain cytochromes, instead of Fe2+. This could disturb the functioning of the cellular respiratory chain, leading to an incomplete reduction of O2 with formation of free oxygenated radicals, reduction in the energy supply, and disturbance of the cytochromes renewal mechanism. All of these phenomena could accelerate cellular aging and explain the lack of efficacy of the chelating agents towards Mn neurotoxicity (Parkinson's syndrome).     

In vivo release of neuronal histamine in the hypothalamus of rats measured by microdialysis

Summary Using an in vivo intracerebral microdialysis method coupled with an HPLC-fluorometric method, we investigated the extracellular level of endogenous histamine in the anterior hypothalamic area of urethaneanaesthetized rats. The basal rate of release of endogenous histamine in the anterior hypothalamic area measured by this method was 0.09 + 0.01 pmol/20 min. When the anterior hypothalamic area was depolarized by infusion of 100 mM K⁺ through the dialysis membrane or electrical stimulation at 200 A was applied through an electrode implanted into the ipsilateral tuberomammillary nucleus, histamine release increased to 175% and 188%, respectively, of the basal level. These increases were completely suppressed by removal of extracellular Ca²⁺. The basal release of histamine was also suppressed after infusion of 10^–6 M tetrodotoxin or i.p. administration of 100 mg/kg of -fluoromethylhistidine. On the other hand, 3-fold increase in the basal release was observed after i. p. administration of 5 mg/kg thioperamide. These results clearly indicate that both the basal and evoked release of histamine measured by our method are of neuronal origin. Send offprint requests to T. Mochizuki at the above address