EFFECTS OF LIPOSOME-ENTRAPPED D-MYO-INOSITOL 1,4,5-TRISPHOSPHATE AND D-MYO-INOSITOL 1,3,4,5-TETRAKISPHOSPHATE IN THE ISOLATED RAT AORTA

This study examined the effects of D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P-3)- and D-myo-inositol 1,3,4,5-tetra-kisphosphate (Ins(1, 3,4,5)P-4)-loaded liposomes upon the contractile activity of vascular smooth muscle, using the isolated (endothelium removed) rat aortic rin g as an in vitro model. While control liposomes had no effect, the adm inistration of Ins(l,4,5)P-3-containing liposomes contracted the smoot h muscle preparation. Furthermore, a similar effect was seen with the administration of Ins(l,3,4,5)P-4-filled liposomes but, in this case, the rings developed a significantly higher level of active tension. Pr etreatment of the aortic preparation with heparin-loaded liposomes blo cked the contractions induced by both Ins(1,4,5)P-3- and Ins(l,3,4,5)P -4-containing liposomes.