Table 1.

Resting dimension of isolated ductus arteriosus from wild-type and COX-deficient term foetal mice

Dimension (μm)	Wild-type (n=25)	COX1−/− (n=8)	COX2−/− (n=16)	COX2+/− (n=11)
Internal diameter	177±3	162±4†	155±4††	157±4††
Vessel length*
Short side	522±8	530±19	466±13††	475±17††
Long side	542±8	548±19	483±13††	488±17††
Wall thickness	18±0.6	21±0.7	20±0.6	19±0.7

Values are mean±s.e.m.

^*Vessel length of the ductus arteriosus is uneven because of its insertion into aorta at an angle. Short side was taken for normalisation of internal circumference and calculation of tension output (see In vitro studies).

^†vs wild-type, P<0.05 (Student's t-test);

^††vs. wild-type, P<0.01 (Student's t-test). Note that, in spite of its overall smaller size, the COX2−/− ductus was outwardly normal on light microscopy and had, specifically, a well-developed muscle layer (C. Ackerley and F. Coceani, unpublished data).