title: Comparative effects of angiotensin-(1-7) and angiotensin II on piglet pial arterioles.
abstract: OBJECTIVE
  Recent investigations indicated that degradation fragments of angiotensins could be involved in the regulation of the cerebral circulation and that their effects might be mediated by prostaglandins. The present study was designed to examine the effect of angiotensin-(1-7), a major endogenous heptapeptide fragment, on cerebral arteriolar diameter and compare it with the octapeptide angiotensin II, and further to determine whether prostaglandins mediate their effects.
  
  
  METHODS
  Newborn, anesthetized pigs were equipped with a closed cranial window, and the diameter of one pial arteriole was measured using intravital microscopy.
  
  
  RESULTS
  Topical application of angiotensin-(1-7) (n = 9) increased the diameter by 6.8 +/- 5.3% (mean +/- SEM), 10.4 +/- 5.2%, 14.3 +/- 5.9%, and 17.5 +/- 7.7% (P < .05) at 10(-7), 10(-6), 10(-5), and 10(-4) mol/L, respectively (baseline, 94 +/- 3 microns). Topical application of angiotensin II (n = 8) increased the diameter by 9.6 +/- 7.0%, 9.6 +/- 7.6%, 11.3 +/- 8.4% (P < .05), and 5.5 +/- 7.9% at 10(-7), 10(-6), 10(-5), and 10(-4) mol/L, respectively (baseline, 94 +/- 5 microns). After administration of indomethacin (5 mg/kg IV), which did not significantly change the baseline arteriolar diameter, neither angiotensin-(1-7) at 10(-4) mol/L nor angiotensin II at 10(-5) mol/L caused significant vasodilation.
  
  
  CONCLUSIONS
  The results indicate that angiotensin-(1-7) is a modest dilator in the cerebral circulation, as is angiotensin II, and that prostaglandins may mediate responses.
authors.affiliation: Department of Physiology and Pharmacology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27157-1083.
authors.forename: W
authors.initials: W
authors.lastname: Meng
authors.forename: D W
authors.initials: DW
authors.lastname: Busija
mesh_terms: D000803:Angiotensin I; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001160:Arterioles; D002536:Cerebral Arteries / Q000187:drug effects*; D005260:Female; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology*; D010841:Pia Mater / Q000098:blood supply*; D011453:Prostaglandins / Q000502:physiology; D013552:Swine; D014665:Vasodilator Agents
chemical_list: D010446:Peptide Fragments; D011453:Prostaglandins; D014665:Vasodilator Agents; D000804:Angiotensin II; D000803:Angiotensin I; C118790:angiotensin I (1-7); D007213:Indomethacin