The action of extracts of the pituitary body / by H.H. Dale.

  • Henry Hallett Dale
Date:
[1909?]
Catalogue details

Licence: Public Domain Mark

Credit: The action of extracts of the pituitary body / by H.H. Dale. Source: Wellcome Collection.

    21/26 (page 445)
    diuresis without any perceptible rise of blood-pressure. While such an observation, which 1 have been able repeatedly to contirm, sufficiently disproves the statement that the diuresis is secondary to and runs parallel to the actual rise of systemic pressure, it does not remove the possibility of the dependence of the diuresis on vascular effects. A redistribution of the blood in the system, caused by the comparative irresponsiveness of the renal arterioles, is conceivable without actual rise of general systemic pressure, especially if the arterial constriction is accompanied by weakening of the heart’s action, due to the depressor constituent which the extract always contains, the action of which, moreover, is much more evident in the case of a second injection. The differential action of enzymes and oxidation on the supposed pressor and diuretic principles, alleged by Schafer and Herring, has not been confirmed in my experiments. On the contrary I have found that whatever destroyed one action destroyed both. Their other evidence for the existence of two principles seems to me also inadequate. They lay stress on the difference in the time relations between the two effects and the relatively greater effect of second injections on diuresis. The difference in time-relations of a diuretic and pressor effect is, however, a familiar phenomenon in cases where there can be no question of the presence of more than one active principle. If strophanthin, for example, be injected intravenously into a dog or cat, the immediate effect on the diuresis is usually a distinct retardation : later, as the rise of arterial blood-pressure passes off, there is generally a secondary acceleration which often persists after the blood-pressure has regained its original level. A similar sequence of events was recently observed by R. P. Laidlaw and myself in experiments, in course of publication, on the action of a pure, crystalline active principle from Apocynum. Such a difference in time-relations cannot, therefore, be accepted as necessitating the presence of two principles. The relatively greater efficacy of a second injection in causing diuresis as compared with its pressor effect can also be interpreted in another way, as indicated above. The blood-pressure tracing is complicated by the presence of the heart-depressing principle : it is not a fair index of the degree of vaso-constriction in this instance. An apparently greater relative efficacy of second injections can also be observed in the case of the uterus, when the effect on that organ is compared with that on the arterial pressure. I have frequently seen, as the result of a second injection, marked contraction of the uterus accompanying a very slight or no rise of blood-pressure.