with antigens or histamine, the anticipated inhibitory effect of a beta adrenergic agonist or theophylline could not be demonstrated. The bronchial challenge model can also be used in humans as illustrated by the following two studies. Although they both include beta} adrenergic agonists, the results can probably be extrapolated to the more selective beta, group. In the first, 17 asthmatic patients were enlisted in a double-blind study designed to determine the blocking effect of SCH 1000 (an atropine analogue) , isoproterenol and the combination compared to placebo on serial concentration of aerosolized histamine and methacholine. Patients met the criteria for selection as recommended by the standardization panel on bronchial inhalation challenge. Two inhalations were used since they represent therapeutic doses. An analysis of the results illustrated in Figure 1 shows that the combination of isoproterenol and SCH 1000 was significantly better than either agent alone in blocking both methacholine and histamine inhalations. Interestingly, although the combination produced a significant bronchodilator effect, at all time periods for all pulmonary function measured, the combination showed no significant effect on heart rate, systolic or diastolic blood pressure. The last study employed approximately 20 individuals and was designed to measure the blocking effect of ephedrine and aminophylline. Although standard doses of aminophylline were employed, (6 mg/kg as a single dose) the dose of ephedrine was relatively high (1 mg/kg), but not exceeding 100 mg of ephedrine single dose. The "old" method of bronchial inhalation challenges with varying numbers of breaths (Spector SL, et at: J Allergy Clin Immunol 56:308, 1975) was employed. Table 1 shows the results. The data are expressed as the mean percentage of difference in the forced expiratory volume in 1 second (FEV1) in the same number of breaths of either methacholine and/or histamine with and without ephedrine and aminophylline. Ephedrine showed inhibition while aminophylline did not in these bronchial challenge experiments. In summary, more in vivo studies are needed to con6rm the usefulness of in vitro models which purport to explain the biochemical effect of beta adrenergic agents and phosphodiesterase inhibitors. The human models employed emphasize the importance of the dose of medication employed, as well as the procedures used to demonstrate the blocking effect. Thus, the three studies presented illustrate the following: (1) no blocking effect with a specific beta, agent or aminophylline in the usual doses could be demonstrated on antigen or histamine skin test reactivity (confirming the work of Galant, SP: J Allergy Clin Immunol 51:11, 1973); (2) high doses of ephedrine can block bronchial inhalation challenges to histamine and methacholine; and (3) although neither the usual dose of a beta adrenergic agonist nor an anticholinergic agent alone could block histamine and methacholine inhalation challenges, the combination was effective.

CHEST 73: 6, JUNE, 1978 SUPPLEMENT

Eftect of Beta Adrenergic Agents On In Vitro Histamine Release and Bronchial Challenge Responses Richard R. Rosenthal, M.D. activity and kinetics both alpha Tandpharmacologic beta agonists have been studied and compared he

of

in our laboratory using both in vivo and in vitro techniques. The in oUTo histamine release technique described by Lichtenstein has provided a means by which the inhibitory effects of various drugs may be studied on antigeninduced histamine release. When graded doses of antigen are added to sensitized cells, the kinetics of the inhibitory effect of various drugs can be compared. We know now that drugs of both beta, and beta, activity, as well as both prostaglandin E} and cholera toxin stimulate adenyl cyclase activity, thereby producing an increase in intracellular cyclic AMP concentration. Only the effect of beta adrenergic agonists can be blocked by propranolol. Whereas the inhibition of histamine release correlates with increased levels of cyclic AMP, studies done in chopped lung fragments by Kaliner, Austin and others have shown that increased intercellular cyclic GMP is associated with augmentation of histamine release. The GTP precursor is converted by membraneassociated guanyl cyclase which may be under the inHuence of cholinergic and alpha adrenergic receptors. Comparison of isoproterenol, epinephrine, norepinephrine, and phenylephrine, the activities of which range from predominantly beta to alpha respectively, con6rmed the fact that inhibition of histamine release seems related to the relative beta activity of a drug. Phenylephrine, considered to be primarily an alpha agonist, had, in fact, a modest inhibitory effect, but did not enhance histamine release. Whereas the beta blocker propranolol diminished the inhibitory effect of these agents, phentolamine, an alpha blocker, did not do so, nor did it enhance histamine release in this system. In oUTo kinetic studies have shown that when the cells are incubated with isoproterenol, there is a very rapid inhibition of histamine release which peaks in about five minutes and is back to baseline by 15 to 20 minutes. The inhibitory effect of isoproterenol reHects the rapid rise and fall of cyclic AMP. Prostaglandin, in contrast, causes rapid but persistent increases in intercellular cyclic AMP with the resulting diminution in histamine release. The third pattern is demonstrated by cholera toxin which causes a slow steady rise in intercellular cyclic AMP, the effects of which, unlike prostaglandin, cannot be eliminated by washing of cells. As observed in the case of the beta agonists the inhibition of antigen-induced histamine release follows the time course of cyclic AMP. Hence adenyl cyclase may be under the influence of drugs of varying beta activity, prostaglandin E h and cholera Reprint requem: Dr. Rosenthal, Good Samaritan Hospital,

Boltimore 21239

WORKSHOP ItO. 1 In

100

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isoproterenol. PGEI and cholera toxin. Whereas both isoproterenol and PGE I have rapid

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activity peaks, the effect of the latter may be attenuated by washing. Stimulation by cholera toxin is slower and not affected by washing.

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III WORKSHOP NO. 1

tive.

CHEST 73: 6, JUNE, 1978 SUPPLEMENT

toxin, each with a characteristic specificity and kinetic behavior. Studies done in the bronchoprovocation laboratory have been directed to much the same assessment of drug activity in vivo. The bronchoprovocation protocol requires dose ranging with inhaled antigen administered to suitable ragweed-allergic patients. The airway parameters of FEV 1 or specific airways conductance are monitored and dose response curves may be constructed. The provocation dose necessary for a 20 percent drop in FEV 1 (PD 20FEV1) 01' a 35 percent drop in specific airways conductance (PDS5 Gaw/VL) may be interpolated and serves as an index of the Patient's bronchial sensitivity to antigen. Inhibitory drugs may be studied in terms of their ability to shift this dose response curve. In this way. the kinetics of isoproterenol were studied. It was determined that when pre-medication with inhaled isoproterenol was given at only one hour before the provocative dose of antigen. it was basically ineffective in tenns of inhibiting the response. This observation correlates very well with pre-incubation studies done with isoproterenol using the in vitro histamine release technique. When isoproterenol was given every 30 minutes during antigen exposure. the dose-response curve was shifted significantly in the direction of increased antigen requirement. Lastly. when isoproterenol is admixed with the antigen given simultaneously. the response to inhaled antigen is completely abolished. When the inhibitory effect of isoproterenol and

CHEST 73: 6, JUNE, 1978 SUPPlEMENT

phenylephrine are compared. our findings are similar to those in vitro. demonstrating that phenylephrine is a weak inhibitor of antigen-induced broocbospasm. Under the influence of propranolol, the inhibitory effect of both isoproterenol and phenylephrine are abolished, but there is no ampli.6cation of the antigen response. It would appear that when the weak beta activity of phenylephrine is blocked by the propranolol, the DOW un0pposed alpha activity still has no effect on either in oitro histamioe release or ira moo bronchospastic response to inhaled antigen. It would appear from these data that alpha adrenergic activity plays little or no role in the immune response of the lung and that therefore, there would be little therapeutic utility to alpha b10cldng drop in the treabnent of asthma. In summary. our experience in both in oitro and in moo systems leads us to cooclude that ~ of beta} and beta, activity inhibit the release of histamioe by virtue of their capacity to stimulate adenyl cyclase. Kinetic studies of beta agonistic drugs reveal a rapid but short-lived increase in interceDuJar cyclic AMP which is reSected in the requirement for beta agonists to be introduced at virtuaDy the same time antigen is presented to the shock organ. Kinetics and relafure pharmacologic activity of selective ~ agonists have not yet been studied in the two systems described, but remain as the next logical steps to be takeQ in the investigation of the relative activity and kinetic behavior' of receptor specific sym-

pathomimetics.

WORISHOP 110. 1 III

Effect of beta adrenergic agents on in vitro histamine release and bronchial challenge responses.

with antigens or histamine, the anticipated inhibitory effect of a beta adrenergic agonist or theophylline could not be demonstrated. The bronchial ch...
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