Cause of the disproportion between the vast increase in plasma renin and the only small (if any) increase in blood pressure after manipulation of the submaxillary gland.

The cause of the disproportion between the vast increase in plasma renin concentration and the small, if any increase in blood pressure after manipulation of the submaxillary glands in mice is complex. The increase in plasma renin was found to cause a marked depletion of renin substrate, which however, was relatively so much less than the increase in renin that the (calculated) renin activity was markedly increased. The sensitivity of the vessels to angiotensin had only decreased in about half the animals studied, and even here the tachyphylaxis could not cope with the pronounced increase in plasma renin activity, as shown by a marked decrease in the blood pressure after blockade of the renin system. The finding that blockade of the renin system lowered the blood pressure below the pre-manipulation level made it probable that the vast release of submaxillary renin is followed by release of a depressor substance. The glands are known to contain kallikrein, but with the methods used it was neither proved nor disproved that the manipulation causes a release of kallikrein. Besides the factors studied, compensatory cardiovascular reflexes can play a role for the disproportion between plasma renin and blood pressure.