Invasive and noninvasive uveal melanomas have different adhesive properties.

AIMS: To establish if invasive and noninvasive uveal melanomas have differences in expression of adhesion molecules, and whether their adhesive interactions with the extracellular matrix (ECM) and endothelium vary. METHODS: Cells from an invasive and noninvasive uveal melanoma cell line and hepatic and dermal microvascular endothelial cells were assessed by flow cytometry for adhesion molecule expression. Tumour cell adhesion to ECM substrates (collagens I and IV, fibronectin, laminin, and vitronectin) and endothelial cells was also investigated using a commercially available assay or a fluorescence-based in vitro assay, respectively. The significance of results comparing cell lines was determined using a Student's t-test, whereby P-values of less than 0.05 were taken as significant. RESULTS: alpha1- and alpha4-integrins were not expressed by noninvasive cells, but were detected on invasive cells. The invasive cell line also expressed higher levels of other integrins than the noninvasive line. Correspondingly, invasive cells adhered in higher numbers to ECM substrates and endothelial cells, and for the latter, the difference was highly significant (P<0.001). No preference in adhesion of invasive cells for the hepatic endothelium was observed. CONCLUSIONS: Successful attachment to and migration through the ECM, basement membrane, and endothelium are vital processes involved in malignant progression. Differential expression of alpha1- and alpha4-integrins by invasive and noninvasive cells infers a role for these receptors in invasion, while the ability of invasive cells to adhere more efficiently to the endothelium suggests that this is a critical factor in uveal melanoma invasion.

Pharmacology of antihistamines.

Unlike the classic antihistamines, the new H1-receptor antagonists do not block cholinergic or central H1 receptors and thus do not produce the side effects, such as sedation, impaired psychomotor performance, and excessive mucosal drying, that are commonly associated with the older agents. Important pharmacokinetic and pharmacodynamic differences that exist among this class of antihistamines translate into varying pharmacologic effectiveness. Terfenadine, loratadine, and cetirizine are all rapidly absorbed in healthy and allergic volunteers (peak plasma levels, 2 to 5 hours); astemizole, however, has an initial distribution phase of 2 to 3 days. Further, astemizole has the longest time to relief of symptoms in this class; histamine wheal inhibition is not apparent until the second day of 10 mg dosing and does not peak for 9 to 12 days. In comparison, terfenadine's antihistaminic action peaks at 3 to 4 hours, loratadine's at 4 to 6 hours, and cetirizine's at 4 to 10 hours. However, whereas the recommended dose of loratadine (10 mg) confers 50% wheal inhibition, 60 mg terfenadine produces an 85% to 90% inhibition. In addition, loratadine and cetrizine have apparent dose-related sedative effects.

Pharmacology and toxicology of nonclassical antihistamines.

Within the past five years the introduction of a new class of antiallergy drug, the nonsedating antihistamine, has changed the way allergy sufferers are treated. The first example of this new therapeutic class, terfenadine, is a highly specific H1-receptor antagonist devoid of central nervous system activity. In clinical trials to date involving more than 7,000 allergy patients, terfenadine (60 mg twice daily) has been shown to be unsurpassed in efficacy, to have a rapid onset of action, and to have an incidence of sedation not different from that of placebo and considerably less than that of conventional antihistamines. In addition, results of task performance studies, including on-the-road driving studies, have demonstrated a lack of performance impairment with terfenadine at single oral doses of 60 to 240 mg, or with multiple oral doses of 60 mg twice daily for one week. Furthermore, no interaction has been observed between terfenadine and alcohol or diazepam. Postmarketing surveillance of more than 1 billion patient days has substantiated this remarkably safe and effective clinical profile.

Mouse uterine muscle as a model for studying beta 2-adrenoreceptor mediated relaxation.

Effects of isoprenaline, adrenaline and noradrenaline on contractility were studied in longitudinal strips of mouse and rat uteri in vitro. In mouse uteri, isoprenaline produced an inhibitory effect on spontaneous contractions which was antagonized by propranolol, a nonselective beta-blocker, but not by practolol, a selective beta 1-blocker. Thus, the inhibitory effect of isoprenaline is mediated by beta 2-adrenoreceptor activation. Adrenaline and noradrenaline also inhibited the spontaneous contractions of mouse uteri. In rat uteri, isoprenaline produced only an inhibitory effect whereas adrenaline initially inhibited the force and frequency of contraction but also had a secondary excitatory effect on the frequency which could be antagonized by phentolamine. Noradrenaline had an inhibitory effect on force but had only a negligible effect on frequency of rat uteri. Phenylephrine also reduced the spontaneous contractility of mouse uteri by a beta 2-mediated effect. From results generated in this study, and from the literature, it is concluded that beta 2-adrenoreceptors are predominant in nonpregnant uteri of rodents, especially the mouse, while alpha-adrenoreceptors are predominant in nonpregnant uteri of rabbit, monkey and human.

In vitro and in vivo assessment of the cardiovascular effects of the cardiotonic drug MDL 19205.

Various in vitro and in vivo techniques were used to evaluate the cardiovascular actions of MDL 19205, a new cardiotonic agent. In the anesthetized dog, intravenous administration of MDL 19205 (0.1-1 mg/kg) produced marked increases in cardiac contractile force which were accompanied by small increases in heart rate and minor decreases in blood pressure. These effects were not altered by alpha- or beta-adrenergic receptor blockade, reserpine pretreatment, or bilateral carotid sinus denervation. In isolated cat cardiac tissues, MDL 19205 (10(-5)-10(-3) M) produced a selective inotropic effect relative to isoproterenol and, unlike isoproterenol, was nonarrhythmogenic. Adrenergic beta-receptor or histamine H1-receptor blockade did not modify the inotropic effects of MDL 19205 in guinea pig atria. The vasodilatory effect of MDL 19205 in the canine isolated pump-perfused hindlimb preparation was not significantly attenuated by surgical sympathectomy, alpha- or beta-adrenergic receptor blockade, cholinergic or histaminergic receptor blockade, or indomethacin pretreatment, indicating that MDL 19205 produced direct relaxation of vascular smooth muscle. MDL 19205 was found to be safe and effective when administered acutely in combination with ouabain, hydralazine, nitroglycerin, or furosemide, agents commonly used in the treatment of congestive heart failure. The pharmacological profile revealed by these and other studies suggests that MDL 19205 should be useful in the clinical treatment of congestive heart failure.

Cardiovascular properties of a new cardiotonic agent, MDL 19205.

The cardiovascular properties of a new cardiotonic agent, MDL 19205, were investigated in anesthetized and conscious dogs and in a dog heart-lung preparation. MDL 19205 (0.1-1 mg/kg), administered to anesthetized dogs by intravenous injection, produced a dose-related increase in cardiac contractile force lasting up to 1 h. It also produced a relatively minor increase in heart rate and a brief decrease in blood pressure. These effects did not involve beta-adrenergic receptor stimulation, as they were observed in dogs after a myocardial-depressant dose of propranolol. Given orally to conscious dogs, MDL 19205 (1 and 3 mg/kg) produced a dose-related increase in dP/dt without producing a significant alteration in heart rate or blood pressure. When administered to anesthetized dogs by constant intravenous infusion, MDL 19205 (0.1 mg/kg/min) produced a marked and sustained increase in cardiac contractile force and decreases in blood pressure and left atrial pressure, but did not produce a significant change in cardiac output or stroke volume, indicating an enhancement of cardiac pump function. Intravenous MDL 19205 reversed the hemodynamic characteristics of heart failure produced by propranolol in anesthetized dogs. In addition, it reversed the depressant effect of pentobarbital on cardiac function in a dog heart-lung preparation. These studies show that MDL 19205 is a potent, direct-acting cardiotonic agent in animals.

Characterization of the cardiovascular activities of a new cardiotonic agent, MDL 17043 (1,3-dihydro-4-methyl-5-[4-(methylthio)-benzoyl]-2H-imidazole-2-one).

The cardiovascular actions of 1,3-dihydro-4-methyl-5[4-(methylthio)-benzoyl]-2H-imidazol-2-one (MDL 17043), a new noncatecholamine, nonglycoside cardiotonic agent, were examined in vivo in anesthetized dogs and in vitro in isolated cat atrial and papillary muscle preparations and guinea pig atria. In the anesthetized dog, intravenous administration of MDL 17043 (0.1--1 mg/kg) produced marked increases in cardiac contractile force which were accompanied by minor increases in heart rate and small decreases in blood pressure. These effects were not altered by alpha- or beta-adrenergic receptor blockade, catecholamine depletion produced by reserpine, bilateral vagotomy, or by bilateral carotid sinus denervation. MDL 17043 (10(-5)--10(-3) M) produced positive inotropic effects in isolated papillary muscle and left atrial strips of the cat that were much greater than the positive chronotropic effects seen in the spontaneously beating right atrium of the cat. The in vitro inotropic effects of MDL 17043 in guinea pig electrically driven left atrial strips were not modified by adrenergic beta-receptor or histamine H1-receptor blockade. The vasodilatory effect of MDL 17043 in the canine isolated pump-perfused hindlimb preparation was not attenuated by surgical sympathectomy, alpha- or beta-adrenergic receptor blockade, cholinergic or histaminergic receptor blockade, or by prostaglandin synthesis inhibition, indicating that MDL 17043 produces direct relaxation of vascular smooth muscle. MDL 17043 was found to be safe and effective when administered acutely in combination with ouabain, hydralazine, nitroglycerin, or furosemide, agents commonly used in the treatment of congestive heart failure.

Cardiovascular properties of a new cardiotonic agent: MDL 17,043 (1.3-dihydro-4-methyl-5-[4-(methylthio)-benzoyl]-2H-imidazol-2-one).

The cardiovascular properties of a new noncatechol, nonglycoside cardiotonic agent, MDL 17,043, were investigated in anesthetized and conscious dogs and the dog heart-lung preparation. MDL 17,043 (0.1-1 mg/kg), administered to anesthetized dogs by intravenous injection, produced dose-related increases in cardiac contractile force lasting more than 1 h. It also produced relatively minor and shorter-lasting increases in heart rate, and brief decreases in blood pressure. These effects were not blocked by propranolol. Of these effects, the increase in cardiac contractile force was, by far, the most prominent. the cardiac effects were also observed in the dog heart-lung preparation. When administered to anesthetized dogs by constant intravenous infusion, MDL 17,043 (09.03 and 0.1 mg/kg/min) produced a marked and sustained increase in cardiac contractile force and a sustained decrease in blood pressure without altering heart rate, suggesting a wide separation between the inotropic instrumented dogs, MDL 17,043 (3-30 mg/kg) produced a sustained increase in dP/dt without altering heart rate or blood pressure. It reversed the depressant effect of pentobarbital on the ventricular function curve in the dog heart-lung. When the hemodynamic characteristics of compensated heart failure were produced by propranolol in anesthetized dogs, MDL 17,043 reversed these effects. These studies suggest that MDL 17,043 may have a beneficial effect in the treatment of heart failure.

Terfenadine, the first non-sedating antihistamine.

Alpha-[4-(1,1-Dimethylethyl)phenyl]-4-(hydroxydiphenylmethyl)- piperidinebutanol (terfenadine, RMI 9918, Triludan, Teldane, resp.) is a potent antagonist of histamine H1-receptor-mediated responses both in vitro and in vivo; no anticholinergic, antiserotonergic or antiadrenergic effects can be demonstrated with terfenadine. In vitro mechanism studies suggest that terfenadine antagonizes histamine in a dualistic manner: competitive at concentrations of 3.16 X 10(-8)-1 X 10(-7) mol/l and unsurmountable at concentrations of 3.16 X 10(-7)-1 X 10(-6) mol/l. In vitro and ex vivo experiments have shown terfenadine to associate/dissociate with histamine H1-receptors much more slowly than a classical competitive antihistamine, chlorpheniramine. Ex vivo experiments as well as radioactive disposition/autoradiographic studies have demonstrated that terfenadine or its metabolites do not readily penetrate into the brain, a finding which suggests an explanation for the lack of CNS effects in both animal and human studies. Clinically, terfenadine is effective against perennial allergic rhinitis, acute seasonal allergic rhinitis and allergic skin conditions while being devoid of CNS effects including sedation, psychomotor impairment or interaction with diazepam or alcohol. Thus, terfenadine is a new antihistamine with a completely different and novel profile from the "classical antihistamines" and as such should prove to have significant clinical advantages for the symptomatic treatment of histamine-associated disorders.

A kinetic study of the antihistaminic effect of terfenadine.

Kinetics of the antihistaminic effect of alpha-[4-(1,1-dimethylethyl)phenyl]-4-(hydroxydiphenylmethyl)-1- piperidinebutanol (terfenadine, RMI 9918, Triludan, Teldane, resp.) were examined in the isolated guinea pig ileum and spirally cut tracheal strip preparations. In the isolated guinea pig ileum, terfenadine produced a parallel or competitive shift (3.16 X 10(-8) and 10(-7) mol/l) as well as a nonparallel or unsurmountable shift (3.16 X 10(-7) and 10(-6) mol/l) of the histamine dose response curves. Using the dose ratio test, it was concluded that terfenadine competes at the same receptors as chlorpheniramine, namely, the histamine H1-receptors. The antihistaminic effects of terfenadine, both the competitive and unsurmountable effects, were difficult to reverse by washout techniques whereas the nonspecific effects (against acetylcholine and barium chloride) could be readily washed out. The unsurmountable antagonism of histamine by terfenadine may result from a slow dissociation of terfenadine from the histamine H1-receptor. When terfenadine (2 mg/kg) or chlorpheniramine (2 mg/kg) was administered systemically, either orally or intraperitoneally, to guinea pigs and the antihistaminic effect assessed in vitro (isolated ileal strips and tracheal strips) terfenadine consistently produced a longer duration of action than chlorpheniramine. It is concluded that terfenadine is a potent, selective histamine H1-receptor antagonist; the kinetics of association/dissociation of terfenadine with histamine H1-receptors may account for the long-lasting antihistaminic effect in various animal models.

Effects of clonidine on gastric acid secretion in the rat.

The effect of clonidine on gastric acid secretion was studied in the pylorus ligated stomach (Shay test) and in the perfused stomach of the rat. Clonidine produced biphasic (inhibitory and stimulatory) effects on gastric acid secretion. In the Shay test, clonidine produced only an inhibitory effect on spontaneous gastric acid secretion in a dose-dependent manner (ED50 = 0.042 mg/kg, intraduodenal administration). In the perfused stomach, clonidine in a dose range of 0.625 to 5 mg/kg i.p. slightly increased acid secretion. The secretion, induced by 5 mg/kg of clonidine, was antagonized by cimetidine (10 mg/kg i.p.) but was not affected by phentolamine. Clonidine, 1.25 mg/kg i.p., a dose which had only a slight stimulatory effect, enhanced histamine- and bethanechol-induced secretion. The enhancement of bethanechol-induced secretion was blocked by pretreatment with cimetidine, suggesting histamine H2 receptor stimulation by clonidine. After i.p. (1.25 mg/kg) or intracerebroventricular (i.c.v., 20 and 40 micrograms/kg) administration, clonidine antagonized 2-deoxy-D-glucose-induced acid secretion. Clonidine also inhibited secretion induced by vagal stimulation in anesthetized, vagi-sectioned rats. These results suggest that clonidine had both central and peripheral sites of action. The inhibitory effect on secretion induced by vagal stimulation was blocked by phentolamine (alpha-1 and alpha-2 adrenergic receptor blocker) but not by labetalol (which blocks alpha-1 but not alpha-2 receptors). It is proposed that the inhibitory effect of clonidine is due to its effect on presynaptic alpha-2 adrenergic receptors located on the postganglionic vagal fibers to the stomach. In summary, these data suggest that clonidine inhibited gastric acid secretion by both a central and a peripheral mechanism. As the dose was increased, clonidine also stimulated acid secretion by a stimulation of histamine H2 receptors.

Salicylamide derivatives related to medroxalol with alpha- and beta-adrenergic antagonist and antihypertension activity.

Analogues of medroxalol (1) were prepared in which the carboxamide function, the phenolic hydroxy group, and the aralkylamine side chain were modified. N-alkyl-substituted amide analogues of 1 showed diminishing beta-blocking activity with increasing steric bulk of the alkyl group. This allowed the conclusion that deactivation of the phenolic hydroxy group of 1 by the carbonyl group of the amide function is responsible for the beta-adrenergic antagonistic properties of 1. This conclusion was strengthened by the finding that the phenolic O-methyl analogue 5-[2-[[3-(1,3-benzodioxol-5-yl)-1-methylpropyl]amino]-1hydroxyethyl]-2-methoxybenzamide (13) was found to have enhanced beta-adrenergic blocking activity. The finding that 13 also had decreased alpha-blocking activity compared to 1 indicated that the phenolic hydroxy group of 1 enhances alpha-adrenergic antagonism. The finding that 1 and 13 showed such a large difference in relative alpha- to beta-blocking potency while exhibiting approximately equal antihypertensive activity in spontaneously hypertensive rats was surprising. In indicated that pharmacologic properties other than alpha- and beta-adrenergic blockade may contribute to the antihypertensive activity of medroxalol. One of the analogues in which the aralkylamine side chain of 1 was replaced by a fragment of a known alpha-adrenergic receptor blocker, 2-hydroxy-5-[1-hydroxy-2-[4-(2-methylphenyl)-1-piperazinyl]ethyl]benzamide (22), showed an interesting pharmacologic profile of potential therapeutic usefulness.

Cardiovascular properties of medroxalol, a new antihypertensive drug.

Medroxalol is a new antihypertensive agent that is presently undergoing clinical trial. Its cardiovascular properties were studied using spontaneously hypertensive rats (SHR), anesthetized dogs, and isolated tissues. Medroxalol produced a long-lasting fall in blood pressure when given by the oral route to SHR. It was more potent than phentolamine in antihypertensive effectiveness. Given intravenously to dogs, medroxalol reduced the blood pressure and heart rate of doses that did not greatly reduce cardiac output. The hypotensive effect of medroxalol was reduced but not abolished following alpha- and beta-adrenergic-receptor blockade. Medroxalol inhibited heart rate and blood pressure responses to isoproterenol and phenylephrine in dogs. In vitro medroxalol resembled a competitive antagonist at alpha-adrenergic receptors in rabbit aortic strips (pA2 6.09) and beta-adrenergic receptors in guinea pig atria (pA2 7.73). It was 0.02 as potent as phentolamine at alpha-receptors and 0.09 as potent as propranolol at beta-receptors. It was concluded that the principal action of medroxalol was to produce a fall in blood pressure by decreasing peripheral vascular resistance more than cardiac output. Adrenergic alpha- and beta-receptor blockade alone does more than cardiac output. Adrenergic alpha- and beta-receptor blockade alone does not satisfactorily explain the hypotension. A contribution by an active vasodilatory component appears likely.

Effect of RMI 81968, a combined alpha- and beta-adrenergic receptor blocking agent, on histamine-induced bronchoconstriction in the dog.

The interaction of propranolol and RMI 81968 on histamine-induced bronchoconstriction was studied in the anesthetized dog using the respiratory overflow technique of Konzett and Rössler. Propranolol, 3 and 10 mumol/kg i.v., enhanced histamine-induced bronchoconstriction. In contrast, RMI 81968, at 10 or 30 mumol/kg i.v., had no effect in this test. It is believed that the alpha-receptor blocking component of RMI 81968 prevents the bronchoconstriction induced by beta-adrenergic receptor blockade. The results of this study suggest that RMI 81968 is less likely than propranolol to produce bronchoconstriction in asthmatic patients.

Cutaneous vascular histamine H1 and H2 receptors in the guinea-pig: the histamine skin wheal as a cutaneous vascular model.

The roles of histamine H1 and H2 receptors in histamine skin wheals were studied in the guinea-pig. Intradermal injections of histamine, 0.125--2 micrograms/0.1 ml, produced wheals in a dose dependent manner. Pyrilamine maleate (3.2 mg/kg p.o., pretreatment for 1 hour) produced a dose dependent shift of the histamine wheal dose-response curve to the right in a parallel fashion. Metiamide, 3, 10 or 30 mg/kg p.o., had no effect on the histamine dose-response curve. However, a combination of metiamide (10 or 30 mg/kg) and pyrilamine (3.2 mg/kg) further increased the effect of pyrilamine. It is concluded that both H1 and H2 receptors are involved in histamine-induced wheals in the guinea-pig.