title: Mechanism of the biphasic arteriolar response to angiotensin II.
abstract: Male Sprague-Dawley rats (140-180 g) were anesthetized with alpha-chloralose and urethan. The cremaster muscle with intact blood supply and neural innervation was suspended in a tissue bath containing a modified Krebs solution. With the use of television microscopy the luminal diameters of third-order arterioles (14-32 micron) were measured before and after adding angiotensin II (ANG II, bath concn 10(-6) M). The arterioles responded to ANG II with an initial, transient constriction followed by a more prolonged dilation to a diameter larger than the control diameter. Pretreating the muscle with [Sar1, Ile8]ANG II significantly attenuated both the arteriolar constriction and subsequent dilation induced by ANG II. Treatment of the cremaster muscle with mefenamic acid or indomethacin, inhibitors of prostaglandin synthesis, produced a significant reduction in the diameter of the arterioles and abolished the dilator phase of the arteriolar response to ANG II without preventing the ANG II-induced constriction. These results demonstrate that within the intact microcirculation, ANG II produces both an arteriolar constriction and a dilation that are mediated by specific ANG II receptors. The ANG II-induced dilation of the arterioles appears to be caused by increased prostaglandin synthesis and release.
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001160:Arterioles / Q000187:drug effects; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008528:Mefenamic Acid / Q000494:pharmacology; D008833:Microcirculation / Q000187:drug effects; D009132:Muscles / Q000098:blood supply*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011945:Receptors, Angiotensin / Q000187:drug effects; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014666:Vasomotor System / Q000187:drug effects*
chemical_list: D011945:Receptors, Angiotensin; D000804:Angiotensin II; D008528:Mefenamic Acid; D009638:Norepinephrine; D007213:Indomethacin