The mechanism of ergonovine-induced airway smooth muscle contraction

The mechanism of ergonovine-induced airway smooth muscle contraction

iseiili'iiMtiofi Yuji Sakamoto, M.D.,* J o s ^ h J. Krzanowski, Ph.D., Richard F. Lodc«y, M.D., Robert Duncan, B.S., James B. Poison, Ph.D., and Andor...

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iseiili'iiMtiofi Yuji Sakamoto, M.D.,* J o s ^ h J. Krzanowski, Ph.D., Richard F. Lodc«y, M.D., Robert Duncan, B.S., James B. Poison, Ph.D., and Andor Szentivanyi, M.D. Tampa, Fh. There have been three articles in the clinical literature of ergonovine maleate-induced hronchospasm. The ejfect of the alkaloid on isolated canine tracheal smooth muscle was analyzed to investigate the mechanism of ergonovine-induced airway smooth muscle contraction. Both ergonovine and 5-hydroxytryptamine (5HT, serotonin) contracted the smooth muscle preparations with EC\„s of 1.35 x /O * mollL and 5.06 x /O ' mol/L, respectively. The maximal conlractile response observed with ergonovine was approximately 30% less than that observed with 5HT. Methysergide competitively blocked both ergonovine and 5HT responses with similar calculated pK^ values (8.33 against ergonovine and 8.46 against 5HT} and also similar pA; values determined by Schild plots (8.50 and 8.45, respectively). The relative affinity and efficacy of ergonovine versus 5HT were determined by use of a concentration of the irreversible antagonist, phenoxybenzamine, which partially blocked receptor sites. The calculated affinity of ergonovine was about 16 times higher than that of 5HT. The relative efficacy at EC,00 for ergonovine was 0.2, but at EC,,, it was 41.9 (5HT efficacy = /). Ergonovine 10 " or 10 " moUL shifted the 5HT dose-response curve to the right without reducing the maximal response, but the shift was nonparallel. Blockade of muscarinic (atropine), a,-adrenergic (prazosin), ({-adrenergic (propranolol), H, (pyrilamine), or //., (cimetidine) receptors did not alter ergonovineinduced contraction. These data indicate that ergonovine directly contracts canine tracheal smooth muscle as a result of its combination with 5HT receptors. This effect may result in precipitation of an asthmatic attack in susceptible individuals. (J ALLERGY CLIN IMMUNOL 77:354-64. 1986.)

Ergonovine (ergometrine), an amine alkaloid in the ergot group, has been mainly used in obstetrics to control postpartum hemorrhage.' • More recently, it has been used in a provocative test for coronary spasm inpatients with variant (Prinzmetal's) angina.' •* Pharmacologically, these actions induced by ergonovine are generally considered to be mediated either through a-adrenoceptors or 5HT receptors, although this is still controversial.'^'* There have been three articles of ergonovine-in-

From the Department ol' Internal Medicine. Division of Allergy and Immunology, and the Department of Pharmacology and Therapeutics. College of Medicine, University of South Florida; and Department of Internal Medicine, Section of Allergy and IminunoU)gy. .lames A. Haley Veterans Administration Hospital, Tampa. Fla. Received for publication Sept. 21. 1984. Accepted for publication July 14. 1985. Reprint requests: Yuji Sakamoto, M.D., Department of Internal Medicine. Division of Allergy and Immunology, University of .South Florida, College of Medicine, Tampa, FL .?3612. * Dr. Sakamoto is a faculty member of the Second Department of Internal Medicine, Nagasaki University, School of Medicine, Sakamoto-machi. Nagasaki, Japan.

354

Abbreviations used 5HT; Serotonin, S-hydroxytryptamine K.; Agonist dissociation constant K„: Antagonist dissociation constant RA; Receptor-agonist complex R,: Total number of receptors pA,: Negative log of molar concentration of antagonist in the presence of which the potency of the agonist is reduced by 2 pK„: Negative log of K„ concentration for fc-Cio, t-v-Ml, t-CjiK). Effective 10%, 50%, and 100% of the maximal response

duced asthmatic attacks after its use for prevention of postpartum or postabortion hemorrhage.'"' In one of these cases, a woman died from severe bronchospasm.'" In this context, we previously reported that this alkaloid elicits contractile responses from isolated canine tracheal smooth muscle." The same preparation was used in the present study to analyze the action of ergonovine in more detail. This article describes

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Ergonovine-induced airway muscle contraction 355

NUMBER 2

with or without BLOCKER

with or without BLOCKER

ERGONOViNE IMI

FIG 1. Experimental protocol for determining and comparing contractile responses of canine tracheal smooth muscle to pharmacologic agonists.

the mechanism of ergonovine-induced canine tracheal smooth muscle contraction.

METHODS Canine tracheal smooth muscle preparation These studies were conducted with methods previously described by Anderson et al.'' Mixed-breed dogs weighing 15 to 22 kg were anesthetized with intravenous pentobarbital (30 mg/kg). The entire trachea was excised to the bifurcation and placed in a Krebs-Ringer solution of the following composition (millimole): NaCl, 117.0; KCl, 4.0; NaHCO,, 25.0; MgS04, 2.4; NaH2P04, 1.2; CaCl^, 2.5; and dextrose, 11.0. A smooth muscle strip (2 to 3 by 15 to 20 mm, weighing approximately 40 mg) was dissected from the cartilage, and each strip was mounted in an isolated bath (10 ml of Krebs-Ringer solution, pH 7.4, 38° C, and oxygenated with 95% O2 and 5% CO2). Contractile tension was measured with a Grass (Grass Instrument Co., Quincy, Mass.) FT03 force-displacement transducer coupled to a Grass model 7 polygraph. The tissue was initially loaded with 2 g of tension and equilibrated for 60 minutes until a stable resting tension of 1 to 2 gm was maintained. This resting tension was less than 10% of the maximum active tension generated to acetylcholine (0.85 g/cm^). This is consistent with the L„„ for canine tracheal smooth muscle as reported by Stephens."

Determination of ECso Cumulative contractile concentration-response curves for ergonovine or 5HT in the absence or presence of the blockers were constructed. Responses to ergonovine or 5HT were expressed as percent contraction to a maximal 5HT response that was obtained first on the same strip (Fig. 1). Each concentration-response curve was analyzed by use of logit transformation and linear regression; then the EC50 was calculated from the regression line. The logit is expressed in the equation:

Y' = log. (y)/(100-Y) where Y' is the f)opulatJon logit and Y is the percent contraction compared to its maximal response." '

Determination of the dissociation constant for methysergide The KB was determined for each concentration of methysergide (10"*, 10"', and 10~* mol/L) according to the following equation": KB = B/(dose ratio - 1) where B is the concentration of methysergide, and the dose ratio is obtained from the EC50 of each agonist (ergonovine or 5HT) in the presence of antagonist (methysergide) divided by the EC50 of the agonist control. Methysergide was added for 15 minutes after the first 5HT concentration-response curve; then a second ergonovine or 5HT concentration-response curve was obtained (Fig. 1).

Schild analysis The blockade by methysergide also was analyzed by Schild plots'* in order to examine the type of antagonism and for comparison with the KB. According to the method of Arunlakshana and Schild," if blockade by methysergide is competitive, Schild plots should produce a straight line with a slope of unity, and the pAj value determined from the Schild plot should be the same as the pKg value ( - log KB) determined mathematically.

Determination of KAS and percent receptor occupancy KAS, the reciprocal of which expresses affinity, were calculated according to Furchgott and Bursztyn," Ruffolo et al.'* and Cohen et al." Partial receptor inactivation by an irreversible antagonist, phenoxybenzamine, was ac-

J. ALLERGY CLIN. IMMUNOL. FEBRUARY 1986

3S6 Sakamoto et al.

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conjplished by use of the following procedures: After the first 5HT concentration-response curve, phenoxybenzamine SO '' mol/L was added. After an additional 5 minutes, the maximal response to the agonist was reduced by about 20% to 30%. This reduction was suitable for K^ determination,-" and then tissues were washed five times before the second agonist (ergonovine or 5HT) concentration-response determination. The following relationship was applied for the calculation; 1

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where [A] and [A'| are equieffective concentrations of the agonist (ergonovine or 5HT) in the absence and presence of phenoxybenzamine. respectively, and q is the fraction of receptors not alkylated by phenoxybenzamine. After con1 1 struction of a double reciprocal plot of — versus . ^ |A| lA'l slope (equals -) and intercept were determined by linear regression. From these results, K^ was obtained by the following equation: K, -

(slope - 1) Intercept

Relative affinity of ergonovine to 5HT was determined by dividing the K^ value for 5HT by that for ergonovine.-" Relative efficacy of ergonovine to 3HT was determined from a plot of response versus receptor occupation that was calculated from the respective equilibrim dissociation constant." '"-" Fractional receptor occupancy for the agonists at each concentration was calculated from the following equation;

The 5HT concentration-response curves in the absence and presence of ergonovine were determined to observe interaction between these two agonists. After obtaining a 5HT concentration-response curve, ergonovine (10 ", 10 *, or 10^ mol/L) was added for 30 minutes, and then the second 5HT concentration-response curve was initiated.

Effects of other specific antagonists Specific antagonists, such as atropine, pyrilamine, cimetidine, prazosin, and propranolol, were applied to test their effects on ergonovine-induced smooth muscle contraction.

Pliarmacotogic agents Ergonovine maleate, 5-hydroxytryptamine creatinine sulfate, pyrilamine maleate (mepyramine), atropine sulfate, indomethacin, and DL-propranolol hydrochloride were obtained from Sigma Chemical Co., St. Louis, Mo. Methysergide maleate was donated by Sandoz Pharmaceuticals, E. Hanover, N. J. Prazosin hydrochloride was obtained through the courtesy of Pfizer Laboratories, New York, N. Y., and cimetidine from Smith Kline, and French Laboratories, Philadelphia, Pa.

Statistical analysis The results are expressed as the mean ± SEM or the mean with the 95% confidence interval. The mean of EC,,,, K,, and K„ were calculated by use of the geometric mean according to the method of Fleming et al.-' All lines were determined by linear regression. Statistical comparison between EC,,, values, pKg values, pA, values, and slopes in Schild plots were made by use of Student's t test for paired data. Maximal responses to ergonovine or 5HT in the presence of methysergide, maximal responses to 5HT in the presence of ergonovine, and the slopes obtained from logit transformation were tested by analysis of variance in a oneway layout.

RESULTS Concentration-response to ergonovine and 5HT Both ergonovine and 5HT induced contraction of canine tracheal smooth muscle with EC,(|S of 1.35 X 1 0 - ' mol/L and 5.06 x 1 0 " ' mol/L, re-

VOLUME 77 NUM8ER 2

Ergonovine-induced airway muscle contraction

- •

CONTROL

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x i t n M E T H V S E R G I D E 10 " M

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w i t h M E T H V S E R G I D E 10 ' M

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357

FIG 3. Concentration-response relationships of canine tracheal smooth muscle to ergonovine and 5HT in the presence of methysergide. The 100% response to ergonovine and 5HT were 266.0 ± 38.2 gm/gm of tissue (n = 6) and 423.9 ± 59.2 gm/gm (n = 6) of tissue, respectively. Methysergide was added 15 minutes before a concentration-response curve was determined.

spectively (Fig. 2). With respect to the EC50, ergonovine is more potent than 5HT; however, the maximal response to ergonovine is less than that to 5HT. The maximal response to ergonovine was 69.5 ± 3.5% of the 5HT maximal contraction (5HT maximal at 100% = 465.4 ± 42.2 gm/gm of tissue, n = 12). The response to ergonovine was variable among dogs as observed in the 95% confidence interval of the EC50 that ranged from 1.82 x 10"'" to 9.95 X 10"' mol/L. Serotonin, however, contracted canine tracheal smooth muscle with a relatively constant EC50 value (95% confidence interval: 1.23 X 10"' to 2.08 X lO"" mol/L). Responses to ergonovine were very slow (ti,2 = 61.3 minutes) to reach maximum and very slowly relaxed to the base line after washing tissue, but 5HT responses were more rapid (ti,, = 18.1 minutes). The response characteristics for ergonovine were not influenced by atropine, propranolol, or indomethacin. Antagonism by methysergide Methysergide blocked both the ergonovine and 5HT responses. The ergonovine and 5HT concentration response curves were shifted to the right (Fig. 3, A and B) without significantly reducing the maximal response (Fig. 4, A and B). The EC50 for ergonovine was shifted by methysergide 10"^ 10"', or lO"*" mol/L from 1.61 X 10"* (control for ergonovine) to

7.92 X 10"% 2.25 x 10"', and 1.30 x 10"' mol/L, respectively. Similarly the EC50 for 5HT was shifted by methysergide 10"*, 10"', or 10"" mol/L from 8.71 x 10"' to 3.65 x 10"", 2.61 x 10"\ and 2.08 x 10"* mol/L, respectively. Analysis of both sets of concentration-response data by use of logit transformation demonstrated that the slopes did not statistically differ from the control observations. In addition, the Schild plot slopes (Fig. 5, A and B) were not significantly different from unity, which means that antagonism by methysergide against ergonovine or 5HT was competitive. The calculated KB and pA2 values from Schild plots were obtained to determine if ergonovine and 5HT involve a common receptor (Table I). Agonists acting on the same receptor would be expected to have an identical pAj value and pKg value for its antagonist.'^- '" The pKg values for methysergide were 8.33 ± 0 . 1 1 against ergonovine and 8.46 ± 0.13 against 5HT (n = 6), and the pAj values were 8.50 ± 0.19 and 8.45 ± 0.15 (n = 6), respectively. There were no significant differences between the PKB values (p = 0.54) or pAj values (p = 0.87). These data suggest that 5HT and ergonovine bind to a common receptor. Additionally, the pKe value was not significantly different from the pAz value for each agonist. This also indicates that methysergide competitively antagonized both ergonovine and 5HT.

J. ALLERGY CLIN. IMMUNOL. FEBRUARY 1986

388 Sakamoto et al.

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WG 4. Comparison of maximal contractile responses of canine tracheal smooth muscle to ergonovine and SHT, plus and minus methysergide. For 100% responses, see Fig. 3.

TASLE I, The features of 5HT and ergonovine with respect to the SHT receptor Schild plot Maximal response*

5HT

110.7

Ergonovine

76.5 ± 3.5%

Paired t test

df = i 1 t = 7.786 < 0.001

p Value

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pKn For mathysergkte

pAz For rnethysergide

Slope

8.46 ± 0.13

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1.01 ± 0.05

8.33 ±0.11

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0.90 ± 0.15

df = 5 t = 1.054 0.54

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0.87

* Compared with initial control concentration curve. t95% Confidence interval. Relative afRnify and effl(»cy (Table II) KA for ergonovine or SHT was calculated in experiments involving the use of a partially blocking concentration of the irreversible antagonist phenoxybenzamine that shifted the concentration-response curve of ergonovine or SHT to the right with reduction of the maximal response. The K^ values were 3.48 X lO-" for SHT and 2.97 x 10"' for ergonovine. Relative affinity and percent receptor occupancy

curves were calculated by use of these K^ values. Affinity of ergonovine at SHT receptors appeared to be about 16 times higher than that of SHT. However, in analyzing the data, it is apparent that there are two groups of animals, i.e., high- and low-affinity groups with relative affinities of 37.2 ± 3.8 (n = 3) and 7.6 ± 1.2 (n = 7) (/? < 0.001), respectively. The relative efficacy of ergonovine was determined from the percent receptor occupancy curve (Fig. 6).

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Ergonovine-mduced airway muscle contraction

ERGONOVINE

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FIG 5. Scfiild plots of canine tracheal smooth muscle responses. A, Ergonovine against methysergide. B, 5HT against methysergide.

TABLE II. Comparison of relative affinity and efficacy between 5HT and ergonovine Relative affinity

5HT Ergonovine

3.48 X 10" (5.36 X 10-' - 2.27 X lO"')* n = 10 2.97 x 1 0 ' (2.22 X 10-" - 3.98 x 10")* n = 10

Relative efficacy

High-affinity group

Low-affinity group

1

1

37.18 ± 3.80 n= 3

7.60 ±1.15 n= 7

At ECw of ergonovine

At EC,o of ergonovine

0.19 ± 0.06 n=10

41.85 ± 17.87 n=10

*95% Confidence interval.

The response when ergonovine fully occupied the receptor (percent receptor occupancy = 100%) was approximately equieffective to the response elicited by 5HT with 19% receptor occupancy. The relative efficacy for ergonovine to 5HT was 0.19 at this contractile response. However, these two occupancy curves crossed each other at the occupancy of 5.2%, and ergonovine had a higher efficacy than 5HT at EC|o. Recapitulating, ergonovine at the maximal response had higher affinity and lower efficacy than 5HT but higher affinity and efficacy at low contractile responses. Ergonovine interaction with 5HT The interaction of ergonovine with 5HT was analyzed to confirm that ergonovine is a partial agonist

at 5HT receptors. Since the data reveal that ergonovine stimulates 5HT receptors with a lower maximal response than 5HT, if ergonovine competitively blocks the 5HT-induced response, this would strongly suggest that ergonovine is a partial agonist. Ergonovine, lO"' or 10"* mol/L, caused a slight contraction and a nonparallel shift of the 5HT concentration-response curve to the right without reducing the maximal response (Fig. 7). The slope of the 5HT concentration response in the presence of ergonovine 1 0 * or 10"^ mol/L was much different from that of the 5HT control; 5HT up to 10"' mol/L slightly reversed an induced contraction by ergonovine, 10"' mol/L. However, as the concentration of 5HT was increased above 10"' mol/L, the tissue contracted in a concentrationdependent manner (Fig. 7).

J. ALLERGY CLIN. IMMUNOL. FEBRUARY 1986

360 Sakamoto et al.

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Effects of other blockers Other blockers such as atropine, propranolol, prazosin, pyrilamine, and cimetidine, all of which were used at 10 *• mol/L, failed to alter the response to ergonovine or 5HT. DISCUSSION Ergonovine is used to prevent postpartum hemorrhage. ' - More recently, it has been used in the diagnosis of variant angina' •* and esophageal spasm." The reports of side effects caused by ergonovine have increased in proportion to its clinical use'*"" -^-" (Table HI). Three cases of ergonovine-induced bronchoconstriction were reported in the last 5 years,'" and in one of these cases, the patient died.'" Pharmacologically, ergonovine acts on smooth muscle via a-adrenoceptors and/or 5HT receptors. It also has activity on the central nervous system via dopamine receptors and/or 5HT receptors.' " There have been numerous experimental reports on different tissues but none on tracheobronchial smooth muscle. The present results demonstrate that ergonovine causes contraction of canine tracheal smooth muscle and that this response is mediated by 5HT receptors.

This conclusion is supported by the fact that methysergide, a relatively specific 5HT blocker, competitively antagonized both ergonovine and 5HT responses with similar pKg and pA, values. Other blockers such as atropine (muscarinic), prazosin (a,adrenergic), propranolol (3-adrenergic), cimetidine (H2), and pyrilamine (H,) did not affect the responses to ergonovine or 5HT. A comparison of the pAj value for methysergide on canine tracheal smooth muscle (8.45) with pA, values in other smooth muscle would indicate that the 5HT receptors in canine tracheal smooth muscle are similar to those in canine femoral artery smooth muscle (pAj, 8.52)" but different from those found in canine coronary artery (pAj, 7.84).-"' Several investigators have indicated that there are distinct subtypes of 5HT receptors in different tissues. According to the classic subtypes," M and D, 5HT receptors in canine tracheal smooth muscle appear to belong to the latter group because atropine fails to block these receptors. Constantine and Knott^*^ found the same type of 5HT receptor in guinea pig trachea. Peroutka and Snyder" defined two different subtypes of 5HT receptors in rat brain based on results obtained in ra-

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Ergonovine-induced airway muscle contraction

10 "•

361

10'

CONCENTRATION OF 5HT IMI

FIG 7. Concentration-response relationship of canine tracheal smooth muscle in the absence and presence of ergonovine (10*', 10 ', or 1 0 ' mol/L).

dioligand binding experiments, i.e., SHT, and SHT, receptors. The latter also has been found in peripheral vasculature of rats." '* Krstic and Katusic^'* identified a third pharmacologically distinct type of SHT receptor in rat heart. In our study the average affinity of ergonovine for 5HT receptors was about 16 times higher than for SHT itself. However, on further analysis, two subgroups of animals were identified. The high-affinity group was 37.2 times higher than SHT, and the lowaffinity group was 7.6 times higher than SHT. The capacity of a drug to initiate a response once it occupies receptor sites is termed efficacy,"*" and the ratio of the efficacies of the two agonists on a common receptor is described by the term relative efficacy. This basis of comparison reflects more accurately the relative contractile potency than does the maximum contractile response.'^' '* The relative efficacy of ergonovine to SHT was determined by use of a partially blocking concentration of the irreversible antagonist phenoxybenzamine. By use of the percent occupancy curves, it is estimated that ergonovine has lower efficacy than SHT at EC,oo but a higher efficacy than SHT at ECio, i.e., when ergonovine stimulates SHT receptors at low concentrations, it is more potent than SHT.

Ergonovine stimulates the SHT receptor, but the maximal response is less than that with SHT. Ergonovine also inhibits the response to SHT without reducing the maximal response. This is consistent with the definition of a partial agonist, i.e., the maximal response is less than that produced by a highly active agonist acting on the same set of receptors. It occludes the receptors by competing with the full agonist.*" Ergonovine antagonized SHT, but the concentration response shifts were not parallel. Moreover, the percent receptor occupancy curve of a partial agonist should be parallel to that of a full agonist,'"" but these curves crossed each other (Fig. 6). Finally, the ECjo of a partial agonist should approximate the K^ for it, but this was not the case for ergonovine. These observations indicate that ergonovine is not a typical partial agonist at SHT receptors in canine tracheal smooth muscle. SHT is not believed to play an important role in human bronchial asthma because it is not found in human mast cells,"" and antiserotonergic agents are not effective in clinical management of asthma.''However, SHT receptors have been identified in tracheobronchial smooth muscle of dogs,"^ cats,"" guinea pigs,"' and humans."' There are reports that the inhalation of a SHT solution (1%) provokes broncho-

J. ALLERGY CUN. IMMUNOL. FEBRUARY 1986

382 Sakamoto et al. TABLE III. Serious adverse reaction caused by ergonovine Adverse reactions

Underlyiiig disorder

Bronclioconstriction

Bronchial asthma; postpartum after cesarean section Bronchial asthma; postpartum after cesarean section Bronchial asthma; postabortion

0.25 mg, IV

Angina during provocation test (five cases) Angina during provocation test Postpartum Postpartum (four cases)

0.1 to 0.3 mg. IV

Refractory cororvary vasospasm

Cardiac arrest Hypertension

Dose and route

0.25 mg, IV

0.4 mg X 3, PO

0.05 mg. IV 0.5 mg, IV 0.2 mg, IV or IM

Postpartum after local anesthesia Postpartum

0.2 mg. IM 0.2 mg, IV

Arterial collapse

Pulmonary edema Gangrene of the legs

Postpartum Raynaud's phenomenon; postpartum after cesarean section Postpartum after cesarean section Postpartum

0.5 mg. IV 0.5 mg, IV

OutGOfflC Recovered after aminophylline and hydrocortisone' Died from severe bronchoconstriction'° Recovered after dyphylline, terbutaline, and prednisone" Three died as a result of testing" Acute transmural inferior infarction; recovered" Resuscitated"' Caused severe hypertension in 1.9% (4/210)=' Subarachnoid hemorrhage and resulting aphasia'' Cerebral hemorrhage; died^» Eclamptic fit; recovered"' All peripheral pulses returned in 2 hours-"

0.5 mg, IV

Recovered after diuretics'"

0.2 mg X 18. PO (Ergotrate; Eli Lilly & Co., Indianapolis. Ind.)

Healed after 3 months"

iV ~ intravenously; IM = intramuscularly; PO - by mouth.

constriction in subjects with asthma but not in normal individuals,**" and it is known that patients with malignant carcinoid tumor, in which 5HT plays an important role, may wheeze." Moreover, 5HT released from aggregated platelets may cause bronchoconstriction manifesting wheezing in a patient with pulmonary embolism.'*' Ergot alkaloids have a wide range of bioli^ic activities that vary from animal to animal and from organ to organ in the same animal.' Our results demonstrate that ergonovine directly contracts canine tracheal smooth muscle via 5HT receptors. A similar mechanism cannot be conclusively established in humans by these data alone; however, we speculate that ergonovine may directly contract human tracheobronchial smooth muscle based on our results demonstrating that ergonovine stimulates 5HT receptors and that human tracheobronchial smooth muscle has 5HT receptors. The patient on whom we previously reported'' developed severe asthma within a few hours of receiving ergonovine, This would indicate that the re-

sponse was of the central (early) airway type. These observations make it reasonable to conclude that ergonovine can cause humans to wheeze as reported in the medical literature. Other possible causes of asthma from ergonovine include drug allergy, enhanced response to biogenic amines, or altered hormonal status. Systemic allergic reactions to this drug appear unlikely, since none of the case reports have other symptoms of a systemic allergic reaction such as flush, urticaria, angioedema, abdominal cramping, nausea, vomiting, diarrhea, laryngeal edema, and/or hypotension.'*"" Ergot alkaloids have been reported to enhance the response to bic^enic amines such as histamine and acetylcholine." -'' The enhancing action of these compounds provides a plausable way to explain why ergonovineinduced bronchospasm occurs, since patients with asthma are sensitive to histamine and acetylcholine. It is also known that certain patients become severely ill with asthma during pregnancy, implying that an

VOLUME 77 NUMBER 2

altered hormonal response from pregnancy may exist. All three reported cases of ergonovine-induced bronchospasm were postpartum or postabortion. Our studies indicate ergonovine can cause canine tracheal smooth muscle contraction, and it has a direct effect on the 5HT receptors. Whatever the explanation for ergonovine-induced bronchospasm in humans, this drug should be used with caution in patients who have asthma or a history of asthma and who are postpartum or are undergoing a challenge with ergonovine for esophageal spasm or variant angina. We thank Patricia Claytor for her secretarial assistance. REFERENCES 1. Berde B: Ergot compounds: a synopsis. Adv Biochem Psychopharmacol 23:3, 1980 2. Hofmann A: Historical view on ergot alkaloids. Pharmacology 16(suppl 1):1, 1978 3. Schroeder JS, Bolen JL, Quint RA, Clark DA, Hayden WG, Higgins CB, Wexler L: Provocation of coronary spasm with ergonovine maleate. Am J Cardiol 40:487, 1977 4. Theroux P, Waters DD, AffakiOS, CrittinJ, Bonan R, Mizgala HF: Provocative testing with ergonovine to evaluate the efficacy of treatment with calcim antagonists in variant angina. Circulation 60:504, 1979 5. Muller-Schweinitzer E: The mechanism of ergometrine-induced coronary arterial spasm: in vitro studies on canine arteries. J Cardiovasc Pharmacol 2:645, 1980 6. Holtz J, Held W, Sommer O, Kiihne G, Bassenge E: Ergonovine-induced constrictions of epicardial arteries in conscious dogs: alpha-adrenoceptors are not involved. Basic Res Cardiol 77:278, 1982 7. Cipriano PR, Guthaner DF, Orlick AE, Ricci DR, Wexler L, Silverman JF: The effects of ergonovine maleate on coronary arterial size. Circulation 59:82, 1979 8. Sakanashi M, Yonemura K: On the mode of action of ergometrine in the isolated dog coronary artery. Eur J Pharmacol 64:157, 1980 9. Sellers WFS, Long DR: Bronchospasm following ergometrine. Anaesthesia 34:909, 1979 10. Crawford JS: Bronchospasm following ergometrine. Anaesthesia 35:397, 1980 11. Louie SJ, Krzanowski JJ, Bukantz SC, Lockey RF: Effects of ergometrine on airway smooth muscle contractile response. Clin Allergy 15:173, 1985 12. Anderson WH, Krzanowski JJ, Poison JB, Szentivanyi A: Characteristics of histamine tachyphylaxis in canine tracheal smooth muscle. Naunyn Schmiedebergs Arch Pharmacol 308: 117, 1979 13. Stephens NL: The mechanics of isolated airway smooth muscle. In Bouhuys A, editor: Airway dynamics: physiology and pharmacology. Springfield, 111., 1970, Charles C Thomas, p 199 14. Armitage P: Transformation for proportions. In Armitage P, editor: Statistical methods in medical research. Boston, 1971, Blackwell Scientific Publications, p 355 15. Furchgott RF: The pharmacological differentiation of adrenergic receptors. Ann NY Acad Sci 139:553, 1967 16. Aninlakshana O, Schild HO: Some quantitative uses of drug antagonists. Br J Pharmacol 14:48, 1959

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17. Furchgott RF, Bursztyn P: Comparison of dissociation constants and of relative efficacies of selected agonists acting on parasympathetic receptors. Ann NY Acad Sci 144:882, 1967 18. Ruffolo RR, Rosing EL, Waddell JE: Receptor interactions of imidazolines. 1. Affinity and efficacy for alpha adrenergic receptors in rat aorta. J Pharmacol Exp Ther 209:429, 1979 19. Cohen ML, Fuller RW, Wiley KS: Evidence for S-HT; receptors mediating contraction in vascular smooth muscle. J Pharmacol Exp Ther 218:421, 1981 20. Besse JC, Furchgott RF: Dissociation constants and relative efficacies of agonists acting on alpha adrenergic receptors in rabbit aorta. J Pharmacol Exp Ther 197:66, 1976 21. Fleming WW, Westfall DP, Delalande IS, Jellett LB: G-normal distribution of equieffective doses of norepinephrine and acetylcholine in several tissues. J Pharmacol Exp Ther 181:339, 1972 22. Dart AM, Davies HA, Lowndes RH, Dalai J, Ruttley M, Henderson AH: Oesophageal spasm and angina: diagnostic value of ergometrine (ergonovine) provocation. Eur Heart J 1:91, 1980 23. Buxton A, Goldberg S, Hirshfeld JW, Wilson J, Mann T Williams DO, Overlie P, Olivia P: Refractory ergonovineinduced coronary vasospasm: importance of intracoronary nitroglycerin. Am J Caixliol 46:329, 1980 24. Crevey BJ, Owen SF, Pitt B: Irreversible coronary occlusion related to administration of ergonovine. Circulation 64:853, 1981 25. Browning DJ: Serious side effects of ergometrine and its use in routine obstetric practice. Med J Aust 1:957, 1974 26. Friedman EA: Comparative clinical evaluation of postpartum oxytocics. Am J Obstet Gynecol 73:1306, 1957 27. Casady GN, Moore DC, Bridenbaugh LD: Postpartum hypertension after use of vasoconstrictor and oxytocic drugs. JAMA 172:1011, 1960 28. Ringrose CAD: The obstetrical use of ergot: a violation of the doctrine "primum non nocere" Can Med Assoc J 87:712, 1962 29. Valentine BH, Martin MA, Phillips NV: Collapse during operation following i.v. ergometrine: a case report. Br J Anaesth 49:81, 1977 30. Davies AE, Robertson MJS; Pulmonary oedema after the administration of intravenous salbutamol and ergometrine. Br J Obstet Gynaecol 87:539, 1980 31. Bross W, Czereda T, Cisek T, Kozminski S: Gangrene of the legs after ergotrate by mouth. Lancet 1:85. 1963 32. Muller-Schweinitzer E, Weidmann H: Basic pharmacological properties. In Berde B, Schild HO, editors: Ergot alkaloids and related compounds. Handbuch der Experimentellem Pharmacologie. New York, 1978, Springer-Veriag, p 87 33. Apperley E, Feniuk W, Humphrey PPA, Levy GP: Evidence for two types of excitatory receptor for 5-hydroxytryptamine in dog-isolated vasculature. Br J Pharmacol 68:215, 1980 34. Brazenor RM, Angus JA: Ergometrine contracts isolated canine coronary arteries by a serotonergic mechanism: no role for alpha adrenoceptors. J Pharmacol Exp Ther 218:530, 1981 35. Gaddum JH, Hameed KA: Drugs which antagonize 5-hydroxytryptamine. Br J Pharmacol 9:240, 1954 36. Constantine JW, Knott C: Benzquinamide and the 5-hydroxytryptamine receptors in guinea pig trachea. J Pharmacol Exp Ther 146:400, 1964 37. Peroutka SJ, Snyder SH: Multiple serotonin receptors: differential binding of 'H-5-hydroxytryptamine, 'H-lysergic acid diethylamine, and 'H-spiroperidol. Mol Pharmacol 16:687, 1979 38. Van Hueten JM, Leysen JE, Schuurkes JAJ, Vanhoutte PM:

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# ^ l i ^ of cro^-r^Ns^vlty k^hRH9Mi Tm0^9m ^"^imta mmi Trk^ma Jacob L. f^nas, M.D., Rofer E. Lindtoerg, Ph.D., Tien M. W. Chen, M.S., and GeraMtne C. Meinfce, Ph.D. Tucson, Ariz. In the southern and western sections of the United States, bites from the reduviid bug, commonly Icnown as the kissing bug, genus Triatoma, may induce serious life-threatening allergic reactions. This .study was undertaken to identify the allergens responsible for patient sensitization and to determine the extent of cross-reactivity of these allergens. The Triatoma spp. most commonly encountered in California and Arizona, T. protracta and T. rubida, were obtained, maintained in the laboratory, and dissected to prepare extracts for testing. Extracts were prepared from T. protracta and T. rubida/or .study by RAST, lymphocyte transformation, leukocyte histamine release, and RAST inhibition. Sera and cells were collected from patients who had generalized reactions to Tiiatoma bites. Our results indicate that T. protracta and T. rubida antigens to which patients are sensitized are present in extracts that contain saliva and that human responses are specific for T. protracta or T. rubida, i.e., allergic cross-reactivity could not he demonstrated.

(J ALLERGY CLIN IMMUNOL 77:364-70,

Anaphylactic reactions in man may result from stings from Hymenoptera, particularly bees, wasps.

From the Departments of Internal Medicine and Microbiology and Immunology, University of Arizona College of Medicine, Tuc:^on, .^ri/ Supported in part by Grant AI 16514 from the Allergy and Immunology Institute of the National Institutes of Health. Received for publication April 8, 1985. .'U'cepted for publication July 14, 1985. Reprint requests: Jacob L. Pinnas, M.D., Department of Internal Medicine, University of Arizona, Tucson, AZ 85724.

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1986.)

yellow jackets, hornets, and ants. Life-threatening and fatal reactions may also follow repeated bites from insects in the order Hemiptera, particularly from bites of the reduviid bug, Triatoma, commonly called kissing bug.'"^ The range of Triatoma includes a major portion of the southern United States and Latin America'' as illustrated in Fig. 1. There are at least 15 species of Triatoma in the United States. The two most commonly encountered species in California, Texas, and Arizona are T. protracta and T. rubida. Adult Triatoma are 15 to 30 mm in length and brown to black in color.