Evidence against an increase in circulating pressor material in renal hypertensive rats

¹ Departments of Physiology and Internal Medicine, University of Michigan, Ann Arbor, Michigan
² Department of Physiology and Internal Medicine, University of Michigan, Ann Arbor, Michigan

The role played by circulating pressor substances in the renal hypertensive rat was studied by means of an isovolemic cross-circulation technique which is capable of detecting pressor activity in the blood of rats made hypertensive by continuous infusions of renin or synthetic angiotensin. When rats are made hypertensive by release of a completely occluded renal pedicle, this pressure elevation is transferred to an assay rat cross-circulated from the test animal several minutes after the release of the pedicle clamps. It follows that this form of renal hypertension is humorally mediated. On the contrary, when rats with renal hypertension of over 1 week's duration are cross-circulated no rise in blood pressure results in the assay rat, indicating that the maintenance of the elevated blood pressure in renal hypertension in the rat is not dependent on a circulating pressor material.