Pfluiger's Archiv, LXIV

Transcription

1 THE PHYSIOLOGICAL EFFECTS OF EXTRACTS OF THE PITUITARY BODY. BY E. A. SCHAFER, F.R.S., AND SWALE VINCENT, M.B. (Six Figures in Text.) (From the Physiological Laboratory, University College, London.) Results obtained by previous Observers. Oliver and Schafer' showed that a decoction of the pituitary body of the sheep produces a marked rise of blood-pressure when intravenously injected. The rise of pressure is rapid, its amount varying with the initial pressure. The fall is slow and the maximum pressure is maintained for many minutes if the dose has been sufficient. The rise is due both to contraction of arterioles and augmentation of heart-beats. It occurs in mammals after division of the spinal cord or destruction of the bulb. This indicates that the action is a peripheral one, which is confirmed by the fact that when added to Ringer's circulating fluid and perfused through the blood vessels of a frog which had been pithed the extract greatly diminishes the flow of fluid. The action of the pituitary extracts was found not to be so powerful as that of suiprarenal; the substance is less readily eliminated, so that the effect lasts much longer, and the action upon the heart is different, the intense inhibition amounting sometimes to complete stoppage of auricular action which is observed with suprarenal extract being absent with pituitary. On the other hand, the accelerating action observed with suprarenal extract with cut vagi is not seen with pituitary but may be replaced by a certain degree of slowing. Szymonowicz2 obtained an effect with pituitary extract in two experiments only, and this he states was a slight lowering of the bloodpressure and a quickening of the heart-beat. These effects are quite different from those described by all other observers. Howell' made extracts of both the hypophysis cerebri, or anterior 1 This Journal, XVIII Pfluiger's Archiv, LXIV Journ. of Exper. Medicine, iii

2 88 E. A. SCHAFER AND S. VINCENT. lobe, and the infundibular body, or posterior lobe, and the effects of each were tested separately on dogs. He employed both saline and glycerine extracts. The material used was obtained in a few cases from the dog, but usually from the sheep. The extracts of the hypophysis alone caused little or no perceptible change in bloodpressure or heart rate. With the extracts of the infundibular body, however, the results were very marked and in their main features quite constant. With vagi intact there was prolonged slowing of the heart-beat accompanying increased blood-pressure, while with vagi cut or after atropin there was a marked prolonged rise of bloodpressure with less slowing of heart-beat. Howell also noticed that the result of one dose is to diminish or even annul the action of a second, unless a very considerable time (half-an-hour or more) is allowed to elapse. Cyon' has also noted that the rise of blood-pressure is accompanied by slowing of the pulse. Both these effects he attributes to stimulation of the pituitary body by the extract which has been injected2. He states that stimulation of the hypophysis in the body either electrically or mechanically will produce similar results through the vagi, and that after extirpation of the organ the effects can no longer be produced by injections. We have not performed any experiments either in the direction of stimulation or extirpation of the hypophysis, but the results obtained by intravenous injections of pituitary extract tend in our opinion to point to an explanation different from that offered by Cyon. A similar opinion is held by Biedl and Reiner3. Cleghorn4 has obtained slowing of the isolated mammalian heart on perfusion of the "infundibular" extract. For the purposes of this investigation the pituitary body of the ox has been used. The organ in this animal is of large size, and we have found it an easy matter to separate the infundibular part from the rest. The extracts have been prepared in various ways. Sometimes we have employed preparations from the freshi organ, sometimes after drying. The extracts have been made with water or saline solution (decoction), alcohol, ether, and glycerine. Combinations of these processes and dialysation have also been resorted to. The de- 1 Pflfiger',g Archiv, LXXI Pfi;ger's Archiv, LXXII Pfuitger's Archiv, LXXIII Amer. Journ. of Physiol. II

3 PITUITARY BODY. tailed modes of preparation are similar to those employed previously in the case of the suprarenal bodyl. The dialyzed extracts we find to be active, so that the substances to which the activity is due are not proteids. In most of our experiments a solution equivalent to about one part of the dried material to four of water or normal saline was used, and this has been always filtered previous to injection into the vein (external jugular). The animals employed to test the effects of the extracts have been cats. Chloroform or ether has been used as the andesthetic, followed by morphia and curari, and sometimes also by atropin. Only a few experiments have been made upon the effects which can be produced by the subcutaneous injection of decoctions of the infundibular part of the pituitary. These were performed upon mice and young rats, and (although the dose required was much greater) have shown that the pituitary extracts produce results resembling in a general way those of suprarenal extracts2. They cause quickened respiration, increased heart's action, and ultimately paralysis, commencina in the hind limbs. We confirm Howell's statement that the rise of blood-pressure is produced solely by the infundibular part of the pituitary and not by the hypophysial part. This is not what might have been expected, seeing that the hypophysial is the proper glandular portion, while the infundibular part is developed as a process of the brain. Berkley3 has however observed glandular looking cells in the infundibular portion, suggesting possible secretory activity of that portion, and this observation we find to apply both to ox and sheep pituitary. Our experiments indicate the presence of two principles in the watery decoction and glycerine extract of the infundibular body; having distinct physiological actions. Of these, the one produces a rise, the other a fall, of blood-pressure. They may accordingly be distinguished as the pressor and depressor substances, and their action may be described separately. The pressor substance. This substance, which appears to be the one the action of which was chiefly obtained by Oliver and Schiifer, causes a rise of blood-pressure resembling in a general way that which I Cp. Oliver and Schifer. This Journal, xviii. 1895; also xviii. p ; and Swale Vincent, this Journal, xxii. p Cp. Swale Vincent, loc. cit. 3 Johns Hopkins Hosp. Rep. iv (quoted from Howell). 89

4 90 E. A. SCHAFER AND S. VINCENT. can be produced by the injection of suprarenal extracts. The rise of pressure, as in the case of suprarenal extracts, is partly caused by contraction of arterioles and partly by increased force of heart-beat. That this is the case is shown by the tracing reproduced in Fig. 1, in which the upper curve represents the volume of a segment of intestine included within a plethysmograph, and the second curve, the blood-pressure taken by a cannula in the carotid. It is to be Fig. 1. Effect upon the arterial pressure and intestinal volume of intravenous injection of decoction of infundibular body. Cat under morphia and curari. The timemarking in all the tracings indicates five seconds. noticed in the tracing that the first rise of blood-pressure begins to pass off while the intestinal vessels are still contracting, and that the blood-pressure remains high even when the intestine volume has come back almost to normal. It is therefore evident that another factor is in operation to produce the rise of arterial pressure, and this can only be increased force of heart-beat". 1 The increased force of the heart-beat was proved by Oliver and Schiifer by direct myographic tracings from the mammalian heart. One of these is given in the article " Ductless Glands " in Schaifer 's Text-Book of Physiology, Vol. i

5 PITUITARY BODY. The rise of blood-pressure may, as is seen in Fig. 1, and as Oliver and Schafer found, be uncomplicated by the slowing of the pulse described by Howell, or it may show this feature in a marked mnanner, as is seen in the tracing reproduced in Fig Fig. 2. Effect upon the arterial pressure of intravenous injection of decoction of itifundibular body. Cat. Morphia and curari. Although this was the first injection, the effect, which is very marked, passed off in about four or five minutes so far asi the rise of pressure is concerned. Nevertheless a second dose produces, instead of a rise a marked fall of blood-pressure (absent as; the result of the first injection), which is followed by a very slight secondary rise. Note the increased excursions of the mercury, most marked near the beginning of the falling curve, indicating cardiac inhibition. Whether this slowing is to be attributed to another substance in the extract which we have not succeeded in isolating cannot at present be stated, but the fact that it sometimes fails to show itself, although the rise of blood-pressure may be most marked, points in that direction. It must not be forgotten that with intact vagi it may in part be due to excitation of the cardio-inhibitory cenatre by the greatly augmented arterial pressure or by contraction of the bulbar arterioles and consequent anaemia of the centre. It must however be partly the result IAlthough the actual pulse-beatsj cannot be counted in these reproductions, the slowing is indicated by the increas;ed excursions of the mercury which are well seen at the beginning of the fall of pressure in the curve shown in Fig. 2. Such increased excursions are often erroneously taken to indicate increased force of heart-beat. The regular rhythmic fluctuations of pressure seen in the curves are of course the effect upon the blood-pressure of the artificial respiration.

6 92 E. A. SCHAFER AND S. VINCENT. of a direct action upon the cardiac muscle or its nervous apparatus, since, as Howell has shown, it is still obtainable, although to a less extent, in an animal with vagi cut or after atropini, and Cleghorn has obtained the action upon the isolated mammalian heart. That the rise of blood-pressure is largely produced by the peripheral action upon the arterioles throughout the body was shown by Oliver and Schafer (cf. above, p. 87). This statement we can fully confirm. After the administration of atropin the rise of blood-pressure which is got on intravenous injection of the infundibular extract is enormous, and is accompanied by very little slowing of the pulse (see Fig. 3)2 Fig. 3. Effect upon the arterial pressure of intravenous injection of decoction of infundibular body. Cat. Morphia, curari, atropin. First injection. Note, as compared with Fig. 2, the relatively slight amount of cardiac inhibition at the beginning of the fall. 1 This was also noticed by Oliver and Schaifer. 2 The intestinal effect appears to be purely passive in this tracing, the isolated vessels apparently not having acted with the rest of the vascular system. Several of the plethysmograph curves indicate the production of a slow rhythmic contraction of blood vessels.

7 PITUITARY BODY. This rise of pressure is comparable to that caused by suprarenal extract', but there is an important difference between the action of this "pressor" pituitary substance and that of suprarenal extract, in that a second dose of pituitary, if administered soon after the first, will fail to produce a second similar rise of pressure. (See Figs. 2 and 4.) This is the case whether atropin have been administered or not. The discovery that a second dose of the extract, administered soon after the first, produces little or no effect in raising the blood-pressure is due to Howell. The fact is one of great diagnostic importance, since it serves to differentiate the action of the " pressor" substance of pituitary from that of suprarenal extract, and indeed from that of all other substances having, a marked " pressor " action which we have tried. And it is the more striking because the repeated dose not only does not produce an immediate rise of 93 Fig. 4. Continuation of the experiment of Fig. 3. The numbers 2 and 3 upon the tracing indicate the administration of a second and third dose of the extract after the blood-pressure had come down again to normal. Notice the marked fall, which is followed by a rise very much smaller and less prolonged than as the result of the first injection. pressure, but actually (owing to the presence of the "depressor" substance) causes a marked fall. 1 Cp. Oliver and chiafer. This Journal, xxiii. 1898; xxiv

8 94 E. A. SCHAAFER AND S. VINCENT. Although, as a general statement, it'is true that no rise of blood-pressure is obtained by a second dose of the extract following soon after the first, it is obvious in our tracings, which are taken on a very slowly moving surface, that a delayed rise does usually occur. This slight after-rise succeeds the marked fall which, as just stated, is the characteristic feature of a repeated injection. Both the fall and after-rise are very apparent in the two curves reproduced in Fig. 4, which is a continuation of that given in Fig. 3. We find that the substance which produces the rise of bloodpressure is insoluble in absolute alcohol. The depressor substance. As has been just stated, if a second dose of an infundibular extract be administered soon after the first, little or no rise of blood-pressuire is produced, but on the other hand a Fig. 5. Comparison of the effects of cholin and extract of infundibular body. marked fall (see Fig. 2, and Figs. 4, 5, and 6), and this fall can apparently be repeated as often as desired'. The lowering of the 1 This fall of pressure on repeating the injection is not mentioned by Howell, although he obtained almost constantly, in the dog, a preliminary fall as the result of a first injection. This we have not seen in our experiments, which have nearly all been performed upon the cat.

9 PITUITARY BODY. blood-pressure is due to the second of the two active substances. This "depressor" substance can be approximately isolated as follows. Dried infundibular material is extracted with absolute alcohol, the extract filtered, and the alcohol allowed to evaporate. The residue is treated with ether, the ether extract is filtered, and the ether allowed to evaporate: the residue of the ether extract is then extracted with normal saline. The resulting solution, when injected into the vein, causes a marked fall of blood-pressure without any rise, either before or after the fall. The curve presents a striking resemblance to that caused by cholin. Fig. 5 shows this similarity. In this tracing the first fall of the blood-pressure tracing is due to cholin hydrochlorate (1 c.c. of a 02 p.c. solution); the second to the " depressor" substance of pituitary. It seemed natural to suppose that the pituitary fall is actually due to the presence of cholin in the extract, since cholin is a product obtainable from nervous matter, and the infundibular body 95 Fig. 6. The same after the administration of a small dose of atropin in the same animal as that employed to obtain Figs. 3 and 4, of which this curve is the continuation. The numbers indicate: 5, a fifth dose of decoction of infundibular body; 6 and 7, a first and second dose of cholin hydrochlorate. Notice that instead of the fall shown in Fig. 5 as the result of cholin injection there is produced a slight and evanescent rise.

10 96 E. A. SCHAFER AND S. VINCENT. is mainly composed of grey matter. But, on further investigation, this proved not to be the case, for the action was found to be unaffected by the administration of atropin, whereas the depressant action of cholin is prevented by atropin'. (See Fig. 6.) We conclude, therefore, that the depressor action of cholin is exerted through the cardio-inhibitory mechanism, whereas that of pituitary extract is a peripheral action upon the musculature of the vascular system. Since the infundibular part of the pituitary is to a large extent composed of grey nervous matter, it has been a natural suibject of enquiry whether extracts of nervous substance (e.g. brain) would produce any distinct physiological effects. Subcutaneous injection of very large doses of brain extract produced no appreciable effect upon a dog2. Howell found no specific action as a result of intravenous injection of brain extracts. We have made several experiments in this direction, but cannot yet come to a positive conclusion as to the action of these extracts. A striking result in some of our experiments has been the causation of very extensive irregularities in the blood-pressure curve, but in other cases no effect whatever has been manifested. We feel justified, then, in concluding that there are specific active substances present in the infundibular part of the pituitary body which do not occur in ordinary nervous matter, nor in other tissues and glandular organs. SUMMARY. 1. Extracts of the pituitary body, when intravenously injected, have a marked effect upon the blood-pressure, producing, according to the nature of the extract, either a marked rise or a marked fall. The pituitary body contains, therefore, two active substances, one pressor and the other depressor. Of these the pressor substance is soluble in salt solution and insoluble in absolute alcohol and ether: the depressor substance is soluble in salt solution, in absolute alcohol, and in ether. The active substances are not destroyed by boiling, and are dialysable. 1 Cp. Mott and Halliburton. Proc. Roy. Soc These authors state that after the administration of atropin the effect produced by cholin is a rise of blood-pressure, but they used much larger doses of cholin than we have done (10 c.c. of 0-2 p.c. solution of cholin hydrochlorate). 2 Swale Vin cen t. This Journal, xxii. p

11 PITUITARY BODY. 2. The pressor substance produces its action both upon the heart and upon the peripheral arteries (confirmatory of Oliver and Schiafer). The action of the pressor substance is a prolonged one (confirmatory of Oliver and Schafer), and during the period of its action a second dose is inactive or nearly so (confirmatory of Howell). The action of the depressor substance is evanescent and can be repeated at short intervals. 3. The pressor effect of the extract may be accompanied by cardiac slowing. This is probably in large part incidental to the contraction of arterioles and rise of aortic pressure, but is in part due to direct action upon the peripheral cardiac mechanism (confirmatory of Oliver and Schafer, Howell, and Cleghorn). 4. The active substances are contained only in the infundibular, not in the hypophysial part of the pituitary body (confirmatory of Howell). 5. Subcutaneous injection of the extracts in small mammals causes paralytic symptoms similar to those obtained by injecting suprarenal extracts. 6. The characteristic effects produced by extracts of the infundibular body are probably not due to the grey nervous matter of which this is largely composed (confirmatory of Howell). 97 PiH. XXV. 7W