blood-vessels of the isolated perfused lungs of the rat. Both Hirakawa

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1 : : : THE ACTION OF ADRENALINE, ACETYLCHOLINE, AND HIS- TAMINE ON THE LUNGS OF THE RAT. By P. FoGGIE. From the Physiology Department, University of Edinburgh. (Received for publication 29th October 1936.) TRIBE [1912] found that adrenaline (crystalline, P. D. & Co.) injected into the isolated perfused lungs of the rat caused vasoconstriction, although solutions of adrenaline containing chloretone gave rise to vasodilatation. She concluded that the dilator effect was solely due to the presence of the preservative. Hirakawa [1925], using doses as large as 100 y, failed to obtain any response to adrenaline from the blood-vessels of the isolated perfused lungs of the rat. Both Hirakawa and Tribe used a constant pressure method of perfusion and kept the perfusion fluid and the lungs at body temperature. The only other investigators, as far as we are aware, who have examined this particular action of adrenaline in the rat are Smith and Bennett [1934.] They showed that in the whole animal the action of adrenaline on the pulmonary arterial pressure was to cause an abrupt rise of pressure, but they did not eliminate the possibility that this rise might have been due to increased cardiac activity. In view of these findings it appeared desirable to examine further the action of adrenaline on the lungs of these animals. This paper deals with the effects produced by adrenaline as well as those caused by acetylcholine and histamine. METHOD. The method of perfusion of the isolated lungs of the rat was similar to that described by Daly, Peat, and Schild [1935] for the guinea-pig. The animal was killed by a blow on the head and cannulae were inserted into the trachea, pulmonary artery and left auricle. The animal was then placed in a tank, the temperature of which was kept from C. and the lungs perfused with fluid at a temperature of C. at constant pressure from a Mariotte bottle. With the constant pressure method changes in pulmonary vascular resistance are readily reflected in outflow alterations. A fall in outflow has been interpreted throughout as vasoconstriction, and conversely a rise in outflow as vasodilatation. The pressure in the Mariotte bottle system registered from

2 1226 Foggie 5 to 8 5 cm. saline. The outflow from the left auricular cannula was recorded by means of a Harris [1931] drop recorder. The lungs were respired under positive pressure by means of the respiration pump described by Daly, Peat and Schild [1935]. This pump enables the pressure of inflation of the lungs to be recorded for a short period of time during any phase of the inflation cycle, the lungs collapsing by virtue of their own elasticity. A rise in the level of the respiratory pressure (R.P.) curve indicates bronchoconstriction, a fall bronchodilatation. A glucose-free Tyrode fluid of the following composition was used for perfusion: NaCl 08 g., KC1 002 g., CaCl g., MgCl g., NaHCO3 0 1 g., NaH2PO g. in 100 c.c. distilled water. All drugs for injection were made up in Tyrode fluid, warmed to body temperature, and were never more than 0 1 c.c. in volume. The preparations used were for adrenaline, the crystalline base (B.D.H.); for acetylcholine, crystalline acetylcholine chloride (Hoffmann La Roche Co.); for histamine, crystalline ergamine acid phosphate, the dosage being given in terms of the base. RESULTS. Adrenaline. Dale and Narayana [1935], working on the guineapig's lungs, have shown that adrenaline may cause both dilatation and constriction of the pulmonary vessels. The vasomotor response to adrenaline appeared to depend in part on the condition of the bronchi. Injection of adrenaline always caused vasoconstriction when the respiratory pressure was low, but produced either vasodilatation or vasoconstriction when the respiratory pressure was high, the vasodilator effects being always accompanied by bronchodilatation. These workers suggest that the vasodilatation is a mechanical effect produced by the release of the pressure on the blood-vessels exerted by the contracted bronchial muscles. The response of the blood-vessels and the bronchi in the isolated lungs of the rat to injections of adrenaline is shown by the Table. It will be seen that small doses of adrenaline produce vasodilatation and larger vasoconstriction (figs. 1 and 2), and there is no apparent relationship between the vascular and the bronchial effects. The Table dloes not show what was apparent during the experiments, namely, that bronchodilatation only appeared when the bronchi were already partially constricted. It is clear from these experiments that in the pulmonary vascular system of the rat adrenaline may cause either vasodilation or vasoconstriction in the absence of any effect on the bronchial musculature. In this connexion it has been shown repeatedly in this laboratory that the pulmonary pressor response to adrenaline occurs in dogs irrespective

3 The Action of Adrenaline, Etc., on the Lungs of the Rat 227 of the bronchomotor effects [Alcock, Berry, and Daly, 1935]. In the same species of animal the pulmonary pressor response to sympathetic nerve stimulation is also independent of the bronchomotor response [Daly and Euler, 1932]. The dog and rat pulmonary blood-vessels thus appear to be uninfluenced by adrenaline relaxation of the bronchial FIG. --Isolated perfused lungs (I.P.L.) of rat. In this and succeeding figures top tracing= outflox- drop recorder; 2nd =respiratory pressure (Intrapul-imonary); 3rd =time signal, 30 sec. The figures above drop recor(ler dlenote numnber of drops per mninute. A sinall dose of adrenaiuae (005 (,y) causes xvasodilatation. FIG. 2. I.P.L. Rat. Large (lose of adrenallinle ((P0)5-) causes x asoconstriction. musculature, whereas those of the guinea-pig are passively relaxed [Dale and Narayana It should be mentioned that neither the vasoconstrictor nor the vasodilator effects -ere influenced by the presence of atropine in the perfusing fluid. The effect of a constant infusion of adrenaline AA-as investigated in view of the results obtained by Burn [1931] on perfusing the vessels of the hind limb of the dog. Burn found the presence of adrenaline in the perfusing fluid increased the vascular response of the limb vessels to sympathetic stimulation. In the experiments now to be described injections of adrenaline Aere given during a constant infusion of the

4 228 Foggie EFFECTS OF INJECTION OF ADRENALINE. Dose Vascular Bronchial No. of No. of in y. Effect. Effect. Tests. Expts D D D si. D D si. D D then C not recorded C C C si. D 1 1 0*5 D * C si. D, C,then D 3 3 SI. C 1.0 C D C C D 1 1 2* *5 C *0 C D 3 3 C =constriction; D =dilatation. same drug. Equal doses were injected before and during the infusion with a view to finding out whether the presence of adrenaline in the perfusing fluid would alter the responses. A control experiment in which three injections of 0 5 y adrenaline were given at 15 to 20 minutes apart showed a slight decrease of the response (vasoconstriction) with each succeeding dose. The effect of adrenaline infusion alone at a concentration of 0.2 y per minute was as a rule negligible, but in some cases slight dilatation was observed. In three experiments, doses of y adrenaline were injected before and during infusion of adrenaline. The vasoconstrictor responses during the infusion obtained by the same dose of adrenaline were slightly more than twice the magnitude of the previous responses in each of the three experiments (fig. 3, Expts. I. and III.), so that the enhancement of the adrenaline vasoconstrictor response due to single injections was similar to that observed by Burn on the response to stimulation of the sympathetic nerve supply to the hind limb. In 9 out of 10 experiments the constrictor action of large doses of adrenaline was reversed by the addition of ergotoxine to the perfusing fluid, the concentration being 25 y per c.c. (fig. 3, Expt. II.). Small doses of adrenaline such as normally produce vasodilatation give a diminished vasodilator response in the presence of ergotoxine. Acetylcholine.-The effect of acetylcholine was more pronounced

5 The Action of Adrenaline, Etc., on the Lungs of the Rat 229 "0o C o 11 X co0: 0 0 O;

6 230 Foggie on the bronchial musculature than on the vascular system. Doses of y in general showed no definite effect on the blood-vessels at times there was; a suspicion of vasodilatation (fig. 3, Expt. V.)-but they produced some bronehoconstriction. Larger doses (5-50 y) caused vasoconstrictor effects in addition to the bronchoconstriction (figs. 4 and 5). The vasoconstriction caused by injections of acetylcholine was not affected by addition of ergotoxine to the perfusing fluid; there FIG P.L. Rat. Bronchoconstrietion in the absence of vasomotor effects produced by acetylcholine, 5.0 2'. FIG. 5. I.P.L. Rat. Bronchoconstrietion anti vasoconstriction produced by acetylcholine, 15t0 it. was, however, an enhancement of this effect by infusion of adrenaline (fig. 3, Expt. VI.). It has not been possible with acetylcholine to obtain vascular effects without a concomitant bronchoconstriction. On the other hand, these experiments show that a bronchoconstriction can be obtained independently of vasoconstriction. Histamine.-Daly, Peat and Schild [1935] have shown that the isolated perfused lungs of the guinea-pig are extremely sensitive to histamine. Doses of y histamine produced a marked bronchial and vascular constriction. Compared with the guinea-pig, the isolated perfused lungs of the rat are relatively insensitive to histamine, the smallest dose giving a response being 5 y. Wherever histamine was effective either on the

7 The Action of Adrenaline, Etc., on the Lungs of the Rat 231 blood-vessels or on the bronchi, the result was constriction. With doses of less than 10 y vasoconstriction could be obtained without a bronchomotor response (fig. 6). Doses of 10 y to 1 mg. histamine caused small bronchoconstrictor effects: in no case was complete lung 1F'i1. 6. I.P.L. Rat. Vasoconstriction in the absence of bronchoinotor effects produtc(ed by histamine, 5.0 ;y. rigidity seen, and the effects were not so large as those obtained with corresponding doses of acetylcholine. Moreover, adrenaline infusions potentiated the effect of the histamine vasoconstriction (fig. 3, Expt. IV.). DisCUSSION. Oni tile blood-vessels of the isolated perfused lungs of the rat adrenaline causes weak dilatation with small doses, and vasoconstriction with large doses. The question of the mode of action of adrenaline in causing vasodilatation has been the subject of considerable discussion. Canion and Rosenblueth [1935] found that vasodilatation caused by adrenaline (in the ergotoxinised animal) was not abolished by atropine, was augmented by cocaine, and these workers conclude that adrenaline in causing vasodilatation acts directly and not by liberation of acetyl choline. Similarly in these experiments on the pulmonary blood-vessels of the rat, the vasodilatation caused by the injection of small doses of adrenaline was not affected by atropine, which finding agrees with the conclusion of Cannnon and Rosenblueth [1935] that vasodilatation resulting from adrenaline is not brought about by a cholinergic mechanism. The effect of a constant infusion of adrenaline on the isolated perfused lungs of the rat was shown to increase to some extent the vasoconstrictor response to injections of adrenaline. Burn [1932] found an enhancement of sympathetic excitation effects by a constant adrenaline infusion. His experiments were carried out on the perfused vessels of the hind limb of the dog. Burn advanced the theory that the store of adrenaline wshich is depleted by sympathetic nerve stimulation is replenished by augmenting the concentration of adrenaline in the

8 232 Foggie 232 Fgi blood. The experiments on the rat's pulmonary blood-vessels show, however, that an increase in the concentration of circulating adrenaline may augment the response to injected adrenaline. This suggests at first sight an alternative explanation of Burn's results, namely, that adrenaline actually sensitises the tissue to a sudden increase in the concentration of adrenaline. There are, however, certain objections to this view, which have been pointed out by Dale and Richards [1918], because a rise in the concentration of the blood adrenaline does not always produce a potentiation of adrenaline which is suddenly injected. We ourselves have observed no such phenomenon in the dog's lungs; indeed, single injections of adrenaline in isolated preparations made from those animals give rise to a smaller pressor response if the concentration of circulating adrenaline is increased. In this respect, therefore, the dog vascular system behaves in a similar manner to the perfused vessels of the hind limb of the dog. The pressor potentiation of single injections of adrenaline by adrenaline infusion in the rat's lung is an entirely unexpected result, and indicates a distinct difference in the reactive properties of the blood-vessels as compared with those of the dog's lung. SUMMARY. 1. The effects of adrenaline, acetylcholine and histamine on the blood-vessels of the isolated perfused lungs of the rat were found to be as follows: Small doses of adrenaline (crystalline) cause pulmonary vasodilatation, and large doses cause vasoconstriction. If any effect on the bronchi takes place, it is one of dilatation. Both histamine and acetylcholine cause bronchoconstriction and vasoconstriction, but much larger doses are required to produce these effects in the rat than in the guinea-pig. 2. A constant infusion of adrenaline was found to increase the vasoconstrictor action of single injections of the same drug. 3. The vasoconstrictor response of large doses of adrenaline is reversed by ergotoxine. I wish to thank Professor I. de Burgh Daly for his very generous help throughout this investigation. REFERENCES. ALCOCK, P., BERRY, J. L., and DALY, I. DE BURGH (1935). Quart. J. exp. Physiol. 25, 369. BURN, J. HI. (1932). J. Physiol. 75, 144. CANNON, W. B., and ROSENBLUETH, A. (1935). Amer. J. Physiol. 112, 33. DALE, A. S., and NARAYANA, B. (1935). Quart. J. exp. Physiol. 25, 85.

9 The Action of Adrenaline, Etc., on the Lungs of the Rat 233 DALE, H. H., and RICHARDS, A. N. (1918). J. Physiol. 52, 110. DALY, I. DE BURGH, and EULER, U. S. v. (1932). Proc. Roy. Soc., B, 110, 92. DALY, I. DE BURGH, PEAT, S., and SCHILD, H. (1935). Quart. J. exp. Physiol. 25, 33. HARRIS, D. T. (1931). J. Physiol. 71, 22 P. HIRAKAWA, K. (1925). Acta Sch. Med. Univ. Kioto, 7, 467. SMITH, F. J. C., and BENNETT, G. A. (1934). J. exp. Med. 59, 173. TRIBE, E. M. (1912). J. Physiol. 45, 20 P. VOL. XXVI., NO