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)P3)- and D-myo-inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4)-loaded liposomes upon the contractile activity of vascular smooth muscle, using the isolated (endothelium removed) rat aortic ring as in vitro model. While control liposomes had no effect, the administration of Ins(1,4,5)P3-containing liposomes contracted the smooth muscle preparation. Furthermore, a similar effect was seen with the administration of Ins(1,3,4,5)P4-filled liposomes but, in this case, the rings developed a significantly higher level of active tension. Pretreatment of the aortic preparation with heparin-loaded liposomes blocked the contractions induced by both Ins(1,4,5)P3- and Ins(1,3,4,5)P4-containing liposomes.