Reactivity to Noradrenaline of Aortic Strips and Portal Veins from Spontaneously Hypertensive and Normotensive Rats

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Abstract
To investigate whether vascular smooth muscle of spontaneously hypertensive rats, SHR, (Oka‐moto 1963) displays any hypersensitivity to noradrenaline (NA) as compared to that of normotensive control rats, NCR, helical aortic strips, alternatively portal vein segments, from a SHR and a NCR were mounted in the same organ bath, to which graded NA doses were added. In neither case did the dose‐response curves, expressed as per cent of the maximal responses, reveal any significant difference between SHR and NCR. These in vitro studies are therefore in agreement with the view that the enhanced flow resistance responses, caused by NA (and other vasoconstrictor agents) in SHR as compared with NCR are not the result of any increased sensitivity to NA of the vascular effector cells proper but may rather, as suggested by Folkow et al. (1970), be due to an increased wall/lumen ratio of the SHR resistance vessels.