ENCAPSULATION OF VIP INTO LIPOSOMES RESTORES VASORELAXATION IN HYPERTENSION IN-SITU

The purpose of this study was to determine whether vasoactive intestin al peptide (VIP) elicits vasodilation in the in situ peripheral microc irculation of hamsters with spontaneous hypertension and whether encap sulation of VIP into liposomes modulates this response. Using intravit al microscopy, we found that suffusion of VIP (0.05 and 0.1 nmol) alon e over cheek pouch resistance arterioles of normotensive hamsters elic ited significant vasodilation that was potentiated and prolonged by en capsulation of the peptide into liposomes (P < 0.05). By contrast, VIP (0.5 and 0.1 nmol) had no significant effects on arteriolar diameter in hamsters with spontaneous hypertension. However, encapsulation of V IP into liposomes restored its vasorelaxant effects in hypertensive an imals, although the duration of vasodilation was significantly shorter in comparison with controls (P < 0.05). Empty liposomes had no signif icant effects on arteriolar diameter in either group. These data indic ate that VIP-induced vasodilation in the peripheral microcirculation i n situ is impaired in essential hypertension and that encapsulation of VIP into liposomes restores, in part, this response.