ISOLATED HUMAN CHORIONIC VASCULAR REACTIVITY - TECHNICAL CONSIDERATIONS FOR FRESH PREPARATIONS

1. Sixty chorionic vascular rings from normal term placentas were imme rsed in an organ bath for isometric tension recording to study (A) the contractile response to 120 mM of potassium chloride (KCI) after adju stment and equilibration to 1-5 g of passive tension; and (B) the conc entration response curve to KCI after adjustment and equilibration to the optimal passive tension. 2. Adjustment to 4 g of passive tension e licited the maximal (P<0.007) and the latest (P<0.006) KCl-induced con traction among arterial rings. Venous rings showed the greatest contra ction when adjusted to 3 g, but the differences were not significant e xcept when compared to 1 g of passive tension (P<0.03). 3. The EC50 fo r chorionic arteries and veins was 14.2 and 25.7 mM, respectively (P<0 .003). The maximal contraction was already obtained with 40 mM of KCl. 4. Our results suggest that (A) the optimal passive tension for fresh human chorionic arteries is 4 g; (B) chorionic venous reactivity is l ess influenced by the initial tension; and (C) the optimal concentrati on of KCI to be used as a contracting agent of these tissues is 40 mM. (C) 1998 Elsevier Science Inc.