Changes in the Contractile Response of Arteries and Veins from Hypertensive Rabbits to Sympathetic Nerve Activity: Assessment of Some Postsynaptic Influences

Abstract

Contractile responses to field stimulation of intramural nerves of arteries and veins taken from rabbits made hypertensive by partial constriction of the abdominal aorta have been related to the carotid artery pressure. The increase in contraction of cephalic and short saphenous veins with rise in carotid artery pressure can be accounted for by an increase in sensitivity of the α-adrenergic receptor. The neurogenic contraction of the ear artery increased with carotid artery pressure rise. Changes in some of the extraneuronal factors that influence transmitter distribution and disposition in the tunica media were examined. In hypertensive animals, the percentage of released adrenergic transmitter entering the vessel wall might be expected to decrease due to an increase in medial thickness. However, this percentage was not significantly altered in the ear artery probably due, in part, to a concomitant increase in medial permeablity to the transmitter. Extraneuronal transmitter disposition factors, i.e. extraneuronal uptake, monoamine oxidase, and catechol-O-methyltransferase activity are directly related to the wet weight of the vessel wall. Thus, their contribution to transmitter disposition would be expected to increase with increase in vessel wall thickness and tend to reduce the response to sympathetic activity. As the contractile response increased in the hypertensive vessels

Smooth muscle cell hypertrophy versus hyperplasia in hypertension.

“…The data presented here illustrate two facts about the smooth muscle cells of normotensive Wistar-Kyoto rats relative to those of spontaneously hypertensive rats. First, the increase in aortic (10)(11)(12) in the absence of any increase in cell number as noted by Olivetti et al (13) can be accounted for by changes in cell ploidy.…”

“…e., hypertrophy-or to an increase in cell number-i.e., hyperplasia. Increased cell number has been inferred from increased numbers of vascular smooth muscle cells labeling with [3H]thymidine (8)(9)(10)(11)(12) and from an increase in DNA per unit vessel length (11,12) (14), and the endothelium was removed with a piece of Teflon. Media preparations were used for subsequent isolation of smooth muscle cells and for DNA determinations described elsewhere.…”

Contractile Responses of Aortic and Portal Vein Strips during the Development of DOCA/Salt Hypertension

“…Functional changes o f arteries, on the other hand, have been reported to occur prior to the develop ment o f hypertension (Jones and Hart, 1975;Hansen and Bohr, 1975). Moreover, different investigators have also shown increased contrac tile response o f veins from hypertensive animals (Bevan et al, 1976;Greenberg and Bohr, 1975;Sutter and Ljung, 1977). As well, Sutter and Ljung (1977) reported that in spontaneously hypertensive rats (SH R ) aortic strips retained their responses to noradrenaline (N A) in low calcium (Ca) less well than strips from control animals, whereas portal veins from S H R re tained their responses in low C a better than controls.…”

An Autoradiographic and Pathological Study of Cellular Proliferation in Rabbit Arteries Correlated with an Increase in Arterial Pressure

“…The in vestigation of hypertensive states, both spontaneous and those induced by renal abnormalities, steroid and salt treatment, adrenal regeneration, aortic stenosis, and drugs, in this species has furnished data elucidating mechanisms of this disease. We have used the rabbit as a hypertensive model as the vessels are larger, allowing both functional as well as patho logical and proliferative changes, particularly in arterial smooth muscle cells (VSM cells), to be studied [3][4][5][6].…”