This study examined the effects of adenosine- and adenosine deaminase
loaded liposomes upon the contractile activity of the vascular smooth
muscle, using the isolated, de-endothelised rat aorta ring as in vitro
model. While control liposomes had no effect, intraliposomal adenosin
e (5X10(-3) M) induced contraction of the preparation. Intraliposomal
adenosine deaminase induced partial relaxation of high K+-precontracte
d rings. The adenosine-induced contraction seems to involve Ca2+ influ
x through L-type channels as an essential component, but protein kinas
e C may also have a modulatory role.