Observations on the Pathogenesis of Spontaneous Inherited Hypertension and Constricted Renal-Artery Hypertension in Rats

¹ Department of Medicine, University of Otago, Dunedin, New Zealand

A preparation is described in which blood is taken alternately from a pair of donor rats and perfused at constant rate through the same vascularly isolated, denervated recipient rat hind limb. The preparation, though sensitive to the vasoconstrictor agent released in acute renal hypertension, fails to detect any vasoconstrictor substance either in the blood of rats bred to develop hyper-tension spontaneously or in the blood of rats with chronic renal hypertension.

To study nervous tone in limb blood vessels, an innervated rat hind limb was perfused through a femoral artery with blood taken from the opposite femoral artery. After administration of hexamethonium, weight-corrected hind-limb perfusion pressures of spontaneous hypertensive (B), chronic renal hypertensive (CR), and control (C) rats (all series included) fall to the same average level. Hence, the component of the hind-limb peripheral resistance which is not neurogenically maintained must be of the same order of magnitude in all three groups. In B, CR, and C rats, the perfusion pressure falls after hexamethonium ; all have the same relationship to the height of the blood pressure at the time the perfusion pressure is measured, high blood pressures being associated with high perfusion pressures and low blood pressures with low perfusion pressures. Therefore, since the differences between the hind-limb peripheral resistances of B, CR, and C rats, as measured by the perfusion pressure, are removed by administration of hexamethonium, it follows that they depend upon differences in the neurogenically maintained component of the peripheral resistance. After hexamethonium the blood pressures of B and C rats fall to the same average level.