The Effects of Pressor Drugs and of Saline Kidney Extracts on Blood Pressure and Skin Temperature 1

Abstract

Many pressor substances, including hormones, drugs, and variously prepared extracts of kidney tissue, have been studied intensively to determine their effects on blood pressure and their possible role in the pathogenesis of human hypertension. Many of these experiments were performed on anesthetized animals and observations usually dealt merely with changes of systemic blood pressure. According to recent studies, however, one of the remarkable features of human hypertension is the association of abnormally high arterial pressure with normal peripheral blood flow. When vasoconstrictor tone in the extremities is diminished by warming the body, blood flow in the forearm increases equally in hypertensive and normal subjects (1, 2). It seemed highly desirable therefore to determine whether the action of any of the known pressor substances simulated human hypertension to the extent of producing, in an experimental animal, a rise of blood pressure without reducing peripheral blood flow simultaneously.In order to study the action of pressor substances on peripheral blood vessels it was found necessary to develop a method which (1) did not require anesthesia, (2) excluded variations arising from spontaneous changes in vasoconstrictor tone of nervous origin, (3) avoided trauma of the vessels studied, and (4) the body of the rabbit. Changes of peripheral blood flow were detected by measuring skin temperature. The procedure required no anesthesia and observations could, if desired, be made on the same animal repeatedly on successive days. This paper compares the effects of epinephrine, tyramine, pituitrin, pitressin, ergot derivatives, guanidine and saline extracts of normal rabbit kidney on blood pressure, amplitude of arterial pulsation, and skin temperature of the rabbit's ear. Of the substances tested, a specially treated saline kidney extract was the only one which elevated peripheral blood pressure without simultaneously reducing skin temperature in the ear of the warmed rabbit. This property of raising blood pressure without measurably decreasing peripheral blood flow appears to depend upon a protein-like substance which remains in solution during heating to 560 C., but is precipitated or destroyed by heating to 650 C. METHODSUnanesthetized male rabbits, weighing usually between 2.0 and 2.7 kilos, were used throughout. The animals were fed either purina rabbit chow with miscellaneous greens or a composite food known to be adequate (3). Hair was removed from both ears with a barium sulphide mixture at least twenty-four hours before the animals were to be used. Under ordinary conditions the vessels of the rabbit's ear dilate and constrict intermittently in response to excitement and the need for radiation or conservation of heat. To abolish such variations of vasoconstrictor tone the animals were placed in a metal box with a double wall through which warm water could be pumped continuously from a reservoir. The temperature of the circulating water was controlled by a thermostat, so that the warmth of the box could be ...

The behaviour of the blood pressure in normal and hypertensive rabbits in response to l‐noradrenaline and to ganglion block by hexa‐ or pentamethonium

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