Isolated small uterine arteries from non-pregnant and term pregnant rats exhibit regulatory responses to elevations in extravascular pressure

An adequate blood supply is essential for the maintenance of uterine function and fetal health during parturition. However, labouring uterine contractions will impart compressive forces on small uterine arteries (SUA). We demonstrate that isolated, pressurised rat SUA arteries, pre-constricted with arginine vasopressin or high potassium solution, exhibit regulatory responses to elevations in extravascular pressure (EVP) which maintain internal diameter constant at EVPs of 0-40 mm Hg. This response is endothelium independent and is not modulated by pregnancy. No regulation was observed in calcium free solution. SUA myogenic responses to elevated EVP likely represents a mechanism for limiting reductions in uterine blood flow during uterine contraction.