Functional implications of sole and selective activation of intravascular coronary endothelial hormonal receptors

The purpose of this review is to present evidence that the lumen of the coronary vascular endothelium is an important site of hormonal action. This review is based on work performed for the last eight years in our laboratories. To demonstrate that selective and exclusive activation or blockade of coronary luminal hormonal receptors is feasible, we have covalently bound to microbeads or large size dextrans (2000 kDa) several hormones or their receptor blockers. These large molecular complexes when administered intravascularly because of their size, remain confined to the blood vessel lumen. The cardiac effects of these large size complexes are identical to those induced by their small size counterparts. The hormones we have used are: adenosine, acetylcholine, bradykinin, substance P, testosterone, and vasopressin. Furthermore, we have also determined the endothelial mediators responsible for the cardiac effects of these hormones. These findings demonstrate that intravascular hormone receptors are indeed physiologically functional and important. In summary, our results support the concept that hormonal stimuli confined to the intravascular endothelial surface trigger the endothelium to release messengers that modulate specific target functions of vicinal parenchymal cells.