Effect of recombinant neutral endopeptidase (EC 3.4.24.11) on neuropeptide-mediated nasal fluid secretion and plasma exudation in the rat

The nasal mucosa harbors sensory nerves containing neuropeptides such as substance P (SP), which are released by capsaicin. The neuropeptides are degraded by peptidases, e.g., neutral endopeptidase (NEP) that is present in the nasal mucosa. We studied the effect of enzymatically active recombinant NEP (rNEP) on neuropeptide-evoked secretion of nasal fluid and plasma exudation in rats. rNEP administered intranasally (i.n.) reduced the capsaicin-evoked nasal fluid secretion but failed to reduce the secretion evoked by SP (exogenous) under the experimental conditions used. rNEP reduced the increase in nasal plasma exudation evoked by capsaicin (endogenous neuropeptides). Because rNEP reduced neuropeptide-mediated nasal fluid secretion and plasma exudation in the rat, we suggest that peptidase activity in the nasal mucosa will determine the magnitude of the response to locally released neuropeptides.

Influence of azelastine and some selected drugs on mucociliary clearance

The effect of azelastine and some selected compounds on ciliary beating frequency (CBF) was investigated in vitro using human mucosal samples and in vivo using anesthetized guinea pigs. Further influence of azelastine on mucus secretion was evaluated in mice and on mucociliary clearance in anesthetized rabbits. Azelastine influenced the ciliary beating frequency neither in vitro nor in vivo. Azelastine, similarly to salbutamol, ambroxol, and bromhexine, increased mucus secretion measured by the tracheal output of phenol red. Azelastine dose-dependently enhanced mucociliary clearance measured by elimination of 99mTc-labeled erythrocytes in rabbits. The activity of azelastine proved to be about 10 times stronger than that of bromhexine. Since the ciliary activity remained unchanged under the influence of azelastine, it is likely that azelastine increases the mucociliary clearance by enhancing bronchial secretion. It is possible that the observed increase in mucociliary clearance may contribute to the beneficial effect of azelastine in the treatment of respiratory diseases.

Influence of various adrenergic compounds on plasma potassium levels in conscious dogs and anaesthetized domestic pigs

The influence of various compounds with affinity to beta-adrenoceptors on plasma potassium levels was investigated in conscious dogs and anaesthetized pigs. There was a marked fall, amounting to about 1 mmol/l following salbutamol and pirbuterol but nearly no effect following dobutamine and xamoterol. In dogs the hypokalaemic effect of salbutamol was augmented when prazosin was additionally applied. It is concluded, that the plasma potassium level is reduced mainly by beta 2-adrenoceptor stimulation. Blocking of alpha-adrenoceptors enhanced this effect and should therefore be avoided when beta 2-agonists are used therapeutically.

Effects of the novel beta-adrenergic partial agonist alifedrine on cardiac performance in dogs with acute ischemic left ventricular failure

Acute ischemic left ventricular failure was induced in dogs by coronary embolization with plastic microspheres, resulting in reduced cardiac output (CO), increased left ventricular end-diastolic pressure (LVEDP), pulmonary capillary pressure (PCP), and total peripheral resistance (TPR). Intravenous (i.v.) administration of alifedrine, a beta-adrenergic partial agonist (0.3 mg/kg as bolus and 0.3 mg/kg/h as infusion), significantly improved performance of the failing heart. Left ventricular contractility was increased up to 50%, heart rate (HR) up to 28%, and CO up to 30%. LVEDP, PCP, and TPR were markedly decreased. Myocardial oxygen consumption was increased only to a minor degree despite the positive inotropic effect; coronary flow was augmented up to 26%. Thus, alifedrine in this model markedly improved left ventricular function by balanced stimulation of the myocardium and reduction of pre- and afterload.

Young domestic pigs for the cardiovascular assessment of inotropic drugs. Comparison with dogs

A comparison is made of cardiovascular response to cardiotonic drugs in young domestic pigs and dogs, and the use of pigs as an alternative to dogs in cardiovascular investigations is described.

[The pharmacology of a new cardiosteroid, a partially synthetic derivative of the aglycone hellebrigenin (acrihellin)]

3 beta,5,14-Trihydroxy-19-oxo-5 beta-bufa-20,22-dienolide 3-(3-methylcrotonate) (acrihellin, D 12 316) is according to chemical structure and pharmacological effects a semisynthetic compound of the aglycon hellebrigenin. It is characterized as a cardiosteroid. In isolated organ (Langendorff heart) the positive inotropic effect proved to be stronger in comparison to digoxin. Also in dogs and cats acrihellin increases the contractile force of the myocardium; especially in failing canine heart, it increases the force of contraction (strain-gauge) and velocity of pressure rise (dp/dt max). In classical glycoside test on cat (Hatcher's dose) acrihellin is more effective than digoxin and methyldigoxin on weight basis, equivalent on a molar basis. The therapeutical index of acrihellin is like that of methyldigoxin. In cats and dogs, the compound is absorbed rapidly and almost completely, especially when administered intraduodenally. Herein it is comparable to methyldigoxin, better than digoxin. In cats acrihellin shows a decay rate of 26%. In all investigations performed in order to study central nervous effects after single administration of therapeutical doses no central side-effects could be detected in contrast to methyldigoxin.