CULTURE-PRODUCED SUBENDOTHELIUM .2. EFFECT OF PLASMA, F-VIIIR-WF AND FIBRONECTIN ON INTERACTION OF NORMAL PLATELETS WITH NORMAL AND VONWILLEBRAND PORCINE AORTIC SUBENDOTHELIUM

Culture-produced normal and von Willebrand (vWd) porcine aortic subendothelium (SE) was prepared on glass and fibronectin (FN)-coated surfaces. Washed porcine platelets reacted extensively with normal SE (on glass) as single adherent nonspread and spread (5%) platelets; vWd SE (on glass)-platelet interaction was decreased with no spreading. Normal porcine plasma increased normal SE-platelet interaction 3- to 5-fold and spreading 5-fold (20-30%); vWd SE-platelet interaction was incresed 2- to 4-fold with no spreading. vWd procine plasma did not affect normal or vWd SE-platelet interaction or spreading. Purified porcine Factor VIIIE:WF (0.5-2 U/ml) increased both normal and vWd SE-platelet interaction 2- to 4-fold without increasing spreading. Purified human FN (50-200 .mu.g/ml) did not increase normal or vWd SE-platelet interaction, but increased spreading 5- to 7-fold (25-35%) with normal SE. Factor VIIIR:WF (2 U/ml) plus FN (200 .mu.g/ml) increased normal SE-platelet interaction 4- to 5-fold and spreading 8- to 9-fold (41%) with extensive SE-associated microaggregate formation; vWd SE-platelet interaction was increased .apprx. 6-fold with no spreading. Platelets reacted more extensively with normal and vWd SE prepared on FN-coated surfaces than SE on glass. Normal SE (on FN)-platelet interaction increased 6- to 7-fold and spreading 12-fold (60%); vWd SE (on FN)-platelet interaction increased .apprx. 110-fold with .apprx. 10% spreading. Plasma (normal and vWd) and Factor VIIIR:WF did not significantly increase normal or vWd SE (on FN)-platelet interaction or spreading. FN may act as a spreading factor in SE-platelet interactions.