title: Flow decreases myogenic reactivity of mesenteric arteries from pregnant rats.
abstract: OBJECTIVE
  To determine whether pregnancy alters the response of small mesenteric arteries to increased pressure (myogenic reactivity) and flow.
  
  
  METHODS
  Mesenteric arteries (300 microns) from cycling nonpregnant (NP, n = 6) and late pregnant (20 days, LP, n = 6) Sprague-Dawley rats were dissected and mounted on an arteriograph system designed for the precise measurement of pressure and flow. Myogenic reactivity was measured as the percentage constriction after a pressure increase to 75 mmHg in the absence and presence of flow (60 microL/minute).
  
  
  RESULTS
  In the absence of flow, there was no difference in myogenic reactivity in arteries from NP versus LP animals (NP, 8.4 +/- 1.4%; LP, 11.0 +/- 1.6%; not significant). In the presence of flow, myogenic reactivity was decreased in arteries from LP rats, but was unchanged in arteries from NP rats (NP, 13.2 +/- 1.1%; LP, 2.5 +/- 2.9%; P < .05). The differential group effect appeared to result not from differences in arterial response to changes in pressure or flow alone, but rather from the interaction between pressure and flow.
  
  
  CONCLUSIONS
  These results suggest that pregnancy alters the interaction of the physical forces of pressure and flow on the arterial wall in a manner consistent with decreased vascular resistance.
authors.affiliation: Department of Obstetrics and Gynecology, University of Vermont College of Medicine, Burlington, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Meyer
authors.forename: G
authors.initials: G
authors.lastname: Osol
authors.forename: M
authors.initials: M
authors.lastname: McLaughlin
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D008638:Mesenteric Arteries / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology