Pregnancy-induced alterations of uterine arteriolar reactivity in the rat: observations with a new in vivo microcirculatory preparation.
OBJECTIVE
The aim of this study was to compare reactivity of uterine arterioles in vivo between virgin and gravid rats.


METHODS
In anesthetized gravid and virgin rats circumferential arterioles were observed by videomicroscopy while vasoactive agonists were suffused over the uterus. Arteriolar diameter changes were compared.


RESULTS
Resting and maximum diameters of circumferential arterioles were significantly larger in pregnant animals. Sensitivity to acetylcholine was greater in pregnant animals than in virgin animals (50% effective concentration, 7.1 +/- 0.17 negative log mol/L vs 6.1 +/- 0.32 negative log mol/L), whereas that to phenylephrine was less (50% effective concentration, 5.3 +/- 0.11 negative log mol/L vs 6.0 +/- 0.17 negative log mol/L). Angiotensin II-induced constriction was significantly reduced in pregnant rats only at lower concentrations. Serotonin significantly dilated arterioles in virgin rats (76% +/- 3% of maximum) but caused significant arteriolar constriction in pregnant animals (65% +/- 4% of maximum).


CONCLUSIONS
The in vivo uterine microcirculatory preparation allows measurement of resistance vessels in the intact animal. Although these results differ from some previous reports, differences may be attributable to vessel location or to in vivo versus in vitro conditions.
Alsip
N L
NL
Center for Applied Microcirculatory Research, the Department of Physiology, University of Louisville Health Sciences Center, Louisville, Kentucky 40292, USA. Nancy.Alsip@louisville.edu
Hornung
J W
JW
Henzel
M K
MK
Asher
E F
EF
D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology; D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D018715:Microscopy, Video; D010656:Phenylephrine / Q000008:administration & dosage / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000008:administration & dosage / Q000494:pharmacology; D014599:Uterus / Q000098:blood supply*; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D000804:Angiotensin II; D010656:Phenylephrine; D012701:Serotonin; D000109:Acetylcholine