exposed with cocaine. In some experiments Pernocton, c.c./kg. body-weight, was injected intramuscularly before carrying out local

Transcription

1 THE ACTION OF DRUGS ON THE ISOLATED PERFUSED LUNGS OF THE PIG. By B. PETROVSKAIA. From the Physiology Department, Edinburgh University. (Received for publication 25th June 1939.) THE investigation to be described was undertaken to determine whether isolated perfused lungs of the pig could be used for testing the action of drugs on the pulmonary vascular bed and bronchi, and, if so, how far the pulmonary responses simulated those obtained under similar experimental conditions in other animal species. The experiments were performed during March, April, and May on stock pedigree animals from 3 to 5 months old. METHOD. The animals were bled to death from the common iliac, carotid, or femoral arteries after ansesthetising the region of the artery to be exposed with cocaine. In some experiments Pernocton, c.c./kg. body-weight, was injected intramuscularly before carrying out local anaesthesia. The blood was defibrinated and then passed through the lungs in order to displace the lung blood, which was also defibrinated. The total blood was then used for perfusion of the lungs at constant volume inflow by a Dale and Schuster pump, negative pressure ventilation being carried out by the method described by Berry and Daly [1931]. Each lung was separately perfused by cannulas in the right and left branches of the pulmonary artery, the blood being collected from the slit pulmonary veins into enamel trays draining into venous reservoirs. Cannulm were also tied into the right and left bronchi for subsequent connexion to the tidal air recorders. The lungs having been separated, each was placed in a separate respiratory chamber. Thus it was possible to carry out two separate perfusions on the lungs of a single animal. Records were taken of the pulmonary arterial pressure (P.A.p.) and the tidal air (T.A.) of each lung. RESULTS. In two out of seven experiments the initial passage of defibrinated blood through the lungs caused intense constriction of the pulmonary vascular bed, and in one experiment cedema occurred at this stage. 277

2 278 Petrovskaia In the remaining experiments cedema occurred within 5-20 minutes of the coimmencenment of perfusion, although in some experiments this was not sufficient to prevent a record of the tidal air being obtained. It was remarkable that the onset of cedemaldid not appear to alter the pulmonary arterial pressure. Our experieicie of the dog's perfused lungs is that cedeimia seldom appears before 4-5) hours, and then is associated with a rise in P.A.p. AdcIenaline. Langendorif [1907] and Macht [19141 reported that epinephrine contracts isolated rinog preparations of the pulimoniary artery, and AVillaret, Besan9on anid Vexenat [1929] found that R. E ; L. R. L. A FIG. 1. Pig,?, 21b0 kg. Isolated perfused lungs (I.P.L.); each lung separately perfused. T.A. =tidal air; P.A.p. =pulmonary arterial pressure; R. =right, L. = left lung; S1 =adrenaline, 10 jug. injected into each lung; S2 adrenaline, 5 p,g. injected into each lutng. Interval between S1 and S2 15 min. Time-marker =30 sec. adrenaline relaxes isolated strips of bronchial muscle. Macht also found that ergotoxine reverses the epinephrine constriction of lung arteries. Although only a few bronchial responses have been obtained owing to the early onset of cedema, the bronchodilator action of epinephrine is confirmed (fig. 1). The most interesting feature of the results was that in every experiment the first injection of adrenaline, or first few, elicited a fall in pulmonary arterial pressure, but subsequent injections caused a rise in P.A.p. This phenomenon occurred when the later doses were higher, similar, or lowi-er than the initial dose (fig. 1). The amount of adrenaline injected varied from 1 to 10 ug. Fig. 1 shows that the P.A.p. response is not dependent upon the bronchomotor response. In one experiment the transformation from an adrenaline depressor to pressor response occurred earlier in one lung than in the other B

3 The Action of Drugs on Isolated Perfused Lungs of the Pig 279 (fig. 2). In this experiment adrenaline initially caused a fall in P.A.p. in both lungs. Fig. 2, A and B, show the difference between the two lungs during the changing response of the right lung. In all the experiments ergotoxine reversed the vasopressor effect of adrenaline (fig. 2, C). A B C FIG. 2.-Pig,?, 20.0 kg. (I.P.L.). Each lung separately perfused. Top tr. =right, lower tr. =left lung. S1. S2, and S3 =adrenaline, 10,Ig. injected into each lung. Ergotoxine ethanesulphonate, 17 mg., was added to the blood of both lung perfusions, between B and C. Interval between A and B =6 min.; between B and C = 20 min. Acetylcholine.-In 3 experiments, 22 injections of A.Ch. were made during the later periods of perfusion after adrenaline and ergotoxine had been injected. All the preparations exhibited some cedema, and a T.A. record was obtained on three occasions only. With small doses of A.Ch. (1-10,ug.) the prevailing pulmonary arterial response was a fall, whereas with larger doses (10 pg. and upwards) the pressure rose (Table and fig. 3). Eserine (3-4 mg.) added EFFECT OF ACETYLCHOLINE ON THE PULMONARY ARTERIAL PRESSURE OF ISOLATED PERFUSED LUNGS OF THE PIG. Number of observations. ± l0-100 zg ,ig. upwards pig. after eserine rise; - = fall; 0 =no clhange; + diphasic response.

4 280 Petrovskaia to the perfusate converted a fall in P.A.p. to a rise or potentiated the rise in P.A.p. if present initially. A similar influence of A.Ch. dosage and eserine on the P.A.p. in the dog has been reported by Alcock, Berry, and Daly [1935]. Villaret, Besan9on, and Vexenat [1929], A B C FiG. 3.- Pig, S, 17 7 kg. Perfusion of right lutng. S1 and S3 =A.Ch., 1 0 yg.; S2 =A.Ch., 60,jg. Betwxeen B an(d C, 2-0 img. eserine was addedl to the bloo(l. Interval betwxeen A and B =8 min.; between B and C = 13 min. working on strips of bronchial muscle, found that A.Ch. caused contraction. In fig. 3 it will be seen that in an eserinised preparation 1 0 Mg. of A.Ch. caused a slight bronchoconstriction. Histamine. In one experiment somewhat large doses of histamine were injected. They caused a rise in P.A.p. and a bronchoconstriction (fig. 4). DISCUSSION AND CONCLIJSIONS. The lungs of the pig isolated and perfused witlh the animal's owin blood are not suitable for testing bronchial responses to the injection of drugs. Sooner or later the preparations exhibit oedeila and prevent iueasurement of the tidal air. This stateinent applies to preparations nlade fromn animals bled to death under Periiocton and local anaesthesia. V7ascular responses to drugs are easily obtainable and, in respect of adrenaline, exlhibit a remarkable uniformity from one preparation to another. Adrenaline invariably reduces the pulmonary arterial pressure in freshly perfused lungs, and augments it during later stages of perfusion. It has been reported that a similar phenomenon may on rare occasions occur in the dog [Alcock, Berry, and Daly, 1935]. How far

5 The Action of Drugs on Isolated Perfused Lungs of the Pig 281 the adrenaline pulmonary depressor effect depends upon the maintenance of vessel tone in some parts of the vascular bed, or to physicochemical changes in the blood or lung tissues under the artificial conditions of perfusion, there is insufficient evidence to decide. Fia. 4. Pig, 3, 17-7 kg. Perfusion of right lung. S1 =histamine, 50 jig; S2 =histamine, 100 pg. SUMMARY. In isolated pig's lungs under negative pressure ventilation and perfused at constant volume inflow with defibrinated blood: 1. Adrenaline reduces the pulmonary arterial pressure in freshly perfused preparations and augments it during later stages of perfusion; ergotoxine reverses the pressor effect. Adrenaline dilates the bronchi. 2. Small doses of A.Ch. tend to lower, and larger doses to raise, the pulmonary arterial pressure in ergotoxinised preparations. The bronchi constrict. I wish to express my thanks to Professor I. de Burgh Daly for his advice and encouragement during this work, and to the Moray Endowment Committee, who defrayed the expenses of the research. VOL. XXIX., NO

6 28} The Action of Drugs on Isolated Perfused Lungs of the Pig REFERENCES. ALCOCK, P., BERRY, J L., and DALY, I. DE BURGH (1935). Quart. J. exp. Phy&il. 25, 369. BERRY, J. L., and DALY, I. DE BURGH (1931). Proc. Roy. Soc., B, 109, 319. LANGENDORFF, O. (1907). Zbl. Physiol. 21, 551. MACHT, D. (1914). J. Pharmacol. 6, 13, 591. VILLARET, M., BESANVON, L., and VEXENAT, A. (1929). C.R. Soc. Biol. 100, 806.