Effects of Angiotensin Infusion on Catecholamine Uptake and Reactivity in Blood Vessels

Abstract

The interrelations between angiotensin and catecholamine uptake have been studied in rats. Angiotensin was infused for either 5, 30, or 120 minutes at three dose levels: 1, 12, and 45 ng/kg/min. With short exposures to angiotensin, effects were seen in kidney, uterus, and adrenal gland. These organs had been previously shown to bind the greatest amount of tritiated peptide administered intravenously. In the 5-and 30-minute experiments angiotensin inhibited uptake of either metaraminol or norepinephrine in most tissues, especially at the higher dose levels, with the exception of the adrenal gland where uptake was increased. After the two-hour infusion inhibition of uptake was seen in most organs. When high titer angiotensin II antibodies were administered intravenously, responses to iv angiotensin were abolished. At this stage the uptake of tritiated norepinephrine was increased in kidney, heart, spleen, and vas deferens, while it was decreased in the adrenal gland. To see whether these biochemical findings are related to a physiological role, contractile responses of isolated perfused arteries of rabbits were studied. Angiotensin potentiated the increase in perfusion pressure after the infusion of norepinephrine, while angiotensin II antibodies decreased this response. Thus, it is concluded that angiotensin can modify the uptake and, hence, the inactivation of the sympathetic neurotransmitter and possibly by this mechanism alter the physiological response to norepinephrine and sympathetic stimulation.KEY WORDS norepinephrine uptake blood vessel reactivity angiotensin metaraminol uptake angiotensin antibodies rabbit isolated arteries 11-96

Renal Responses to Slight Elevations of Renal Arterial Plasma Angiotensin Ii Concentration in Dogs

“…In order to study the direct effects of angiotensin I1 on the kidney the indirect effects of angiotensin I1 which can influence renal function should be avoided or controlled. These effects include an increase in arterial pressure (Page & Helmer, 1940), effects on the central nervous system (Ferrario, Gildenberg & McCubbin, 1972;Severs & Daniels-Severs, 1973), effects on peripheral adrenergic activity (McCubbin & Page, 1963;Khairallah et al, 1971), and stimulation of release of aldosterone by the adrenal gland (Laragh et al, 1960). In the present experiments arterial pressure did not increase when angiotensin I1 was infused directly into the renal artery of dogs and no functional changes took place in the contralateral control kidney.…”

Pressor responses to norepinephrine in rabbits with 3-day and 30-day renal artery stenosis. The role of angiotensin II.

“…Sakurai and Hashimoto 15 and Khairallah et al 12 reported that angiotensin II increased the vasoconstrictor effects of norepinephrine in isolated perfused rabbit ears. The response to norepinephrine of the perfused hindlimbs of rats was observed by Sato and Masuyama 16 to be enhanced by angiotensin II.…”

“…Infusions of angiotensin II have been shown to potentiate the vascular effects of sympathetic stimulation or norepinephrine infusion. 12 " 16 Because disturbances of the renal circulation are known to promote renin release, 17 it is possible that the renin-angiotensin system may be involved in the hyperresponsiveness to norepinephrine seen in renal hypertensive animal models.…”