Vascular-derived kinins and local control of vascular tone

RESUMO

The vascular itself, through a complex interplay of endocrine, neurocrine and autoparacrine mechanisms, plays an active role in vascular homeostasis. The endothelial cell senses humoral and hemodynamic changes and respondes by secreting a variety of metabolically active substances that act locally causing either vasodilatation or vasoconstriction. Kallikrein (KK) and the nRNA for KK are present in arteries and veins. Vascular KK releases Kinins from kininogen which circulate in plasma and is also present in vascular tissue. Vascular-derived kinins induce vasodilatation through the release of endothelial compounds ( prostacyclin, EDRFs and cytochrome P-450). Disturbance in the delicate balance between vasodilators and vasoconstrictiors may play a role in the development of hypertension. Vascular kallikrein (VKK) was significantly (P < 0.05) elevated after 2 weeks of development of renovascular and mineralocorticoid hypertension, and blood pressure was only slightly elevated. However, VKK decreased in both experimental models when blood pressure was incresed. It is possible that the increase in VKK in the early stages resulted in incresead local vasodilatory activity, thus counteracting the rise in blood pressure. As hypertension developed, KK was significantly decreased in arteries. The decrease in arterial KK during established hypertension is most likely secondary to high blood pressure....