Proceedings of The Physiological Society

University College Dublin (2009) Proc Physiol Soc 15, PC53

Poster Communications

Vascular reactivity of early pregnancy human placental chorionic plate arteries.

M. Wareing1

1. Maternal and Fetal Health Research Centre, The University of Manchester, Manchester, United Kingdom.

Background: We have previously demonstrated that placental chorionic plate arteries (CPAs) at term exhibit a biphasic (transient contraction followed by maintained relaxation) response on exposure to histamine [1]. Here we wished to determine if early pregnancy CPAs displayed similar vascular reactivity. Method: Placentas (N=5) were obtained following elective medical or surgical termination of pregnancy. Gestational age was estimated from date of last menstrual period and confirmed by ultrasound dating. Biopsies were placed into ice-cold HCO3--buffered physiologic salt solution (PSS). Arteries were dissected from the chorionic plate, mounted onto a wire myograph, normalised at 0.9 of L5.1kPa and equilibrated (37°C; 20 mins; 5%O2/5%CO2 ~7% O2). Contraction was assessed with 120mM potassium solution (KPSS) and the thromboxane-mimetic U46619 (10-10 to 2x10-6M). Histamine hydrochloride (HIS; 10-6M) was added to pre-contracted vessels (EC80 dose of the thromboxane-mimetic U46619 for 30 mins) for 60 mins. Experiments with HIS were also performed in the presence of indomethacin (I; 10-5M) and indomethacin plus Nω-nitro-L-arginine, (IN; both 10-5M). Arterial relaxation to donated nitric oxide (NO) was assessed using sodium nitroprusside (SNP; 10-5M). All data are expressed as median (range). Results: Normalised luminal internal diameters were 486 (210-1008) μm (n=20 arteries). Maximal arterial contraction to KPSS and U46619 was 2.0 (0.4-5.0) kPa and 3.2 (1.2-6.8) kPa (n=20 arteries from N=5 placentas) respectively. HIS induced a biphasic response in pre-contracted CPAs; a transient contraction to 105 (102-118) % of EC80 U46619-induced contraction followed by a maintained relaxation to 95 (23-95) % of EC80 U46619-induced contraction. Contraction and relaxation to HIS alone were not significantly affected by pre-incubation with I or IN (P<0.05; Friedman’s test followed by Dunn’s post hoc test). SNP induced a significant relaxation in pre-contracted CPAs; a maximal relaxation to 37 (2-71) % of EC80 U46619-induced contraction. Conclusion: Our preliminary data suggest that 10-6M HIS elicits a biphasic response in early pregnancy CPAs; the pattern of response is similar to that seen in term CPAs but the size of the responses are reduced compared to term [1]. The ability to assess placental vascular reactivity in early pregnancy is essential for the development of therapeutic agents to treat pathologies associated with increased placental vascular resistance [2].

Where applicable, experiments conform with Society ethical requirements