Blood Pressure of Pregnant Rabbits and its Response to Pitressin. ∗

Abstract

Schockaert and Lainbillon 1 have demonstrated that women in the latter half of a normal pregnancy are relatively insensitive to the pressor action of the postpituitary hormone, and that the blood serum of such women, when mixed with postpituitary hormone has an inhibitory action on the pressor coniponent as compared to the serum of non-pregnant ivonien. These findings have been applied to the study of human eclampsia. 2 This reports an attempt to determine whether such a phenomenon may be demonstrated in the rabbit.

We have found no reports of blood pressure records throughout pregnancy except for the human being, and it was necessary therefore to determine whether iioriiial pregnancy in the rabbit produced any significant alteration of blood pressure. At various intervals through-out pregnancy, a standard dose of pitressin was administered intra-venously to the unanesthetized animal to obtain the pressor response.

The method of Grant and Rothschild 3 was used for measuring the blood pressure on the central artery of the ear of warm, unanes-thetized female rabbits weighing 3 to 4 kg. In one major respect our technic differed from theirs. Measurements were made at intervals of 10 to 15 seconds rather than 1 or 2 minutes. This offered a necessary advantage in enabling us to follow the rather rapid changes of blood pressure which follow the injection of pitressin. By actual tests it was found that the reactive hyperemia resulting from rapid determinations caused a lowering of the blood pressure only on the second reading and not thereafter. Readings were made until 5 consecutive values were found within 4 mm. The mean of these 5 readings was recorded as the resting blood pressure.

Pitressin was injected into the marginal vein of the ear opposite from the blood pressure capsule.