Modification of angiotensin II-induced relaxation by dipyridamole, phthalazinol and aspirin in isolated dog renal arteries.

Abstract

Abstract-Angiotensin(ANG) II-induced relaxations in isolated dog renal and cerebral arteries are postulated to be mediated by the release of prostaglandin (PG) 12 from the arterial wall. In helical strips of dog renal arteries treated with dipyridamole, relaxations induced by ANG II (10-7 M) and exogenously applied PG12 (10-8 M) were potentiated; the potentiation was appreciably greater in the ANG-induced relaxation. Treatment with phthalazinol did not alter the response to ANG II, but significantly potentiated the relaxation induced by PGI2. The ANG-induced relaxations were suppressed or reversed to contractions by aspirin or indomethacin. Combined treatment of dipyridamole with aspirin or indomethacin restored the relaxant response to ANG II, while phthalazinol in combination with aspirin did not restore the response. It may be concluded that the potentiation of responses to ANG II by dipyridamole is associated with increments in the release of PGI2 from the arterial wall and potentiations of the response of arterial smooth muscle to PG12. Dipyridamole appears to increase the production of PGI2 even in the presence of PG synthesis inhibition by aspirin or indomethacin.

Pharmacological evidence for the existence of a local renin‐angiotensin system in porcine interlobar renal arteries

“…These observations suggested that the contractile response to angiotensin II was mediated through enhanced release of arachidonic acid and that end products of both the cyclo-oxygenase and lipoxygenase pathway contribute to the contractile responses of porcine interlobar renal arteries to angiotensin II. Hence, this artery shares the requirement of intact prostaglandin synthesis with renal arteries from dogs, which respond to stimulation by angiotensin II with relaxation that is also indomethacinsensitive (Toda & Yamamoto, 1983;Toda, 1984;Toda et al, 1987;Okamura et al, 1990).…”

Effects of Angiotensin II on Isolated Rabbit Afferent Arterioles

“…In the present experiment, we confirmed Edwards' results. However, interestingly, Toda et al (20,26) reported that Ang II caused relaxation in the helically cut strip of dog renal artery, and this relax ation was mediated by vasodilatory PGs. In fact, isolated AA has the ability to produce vasodilatory PGs (21) and NO (12).…”