Metabolism of serotonin and adenosine. In: Jaffe EA, editor. Biology of Endothelial Cells. Boston: Springer US; 1984. pp. 330-42. [DOI: 10.1007/978-1-4613-2825-4_33]

Localization of vasopressin, serotonin and angiotensin II in endothelial cells of the renal and mesenteric arteries of the rat

The localization of vasopressin, serotonin and angiotensin II in the endothelial cells of renal and mesenteric arteries was investigated using the pre-embedding peroxidase-antiperoxidase technique for electron microscopy. Vasopressin- and serotonin-positive endothelial cells were present in both renal and mesenteric arteries while angiotensin II-positive cells were observed in the mesenteric artery exclusively. Both arteries showed less than 10% immunoreactive cells. The lack of angiotensin II in the endothelial cells of the renal artery suggests that there may be subtle physiological differences between the renal and mesenteric arteries with respect to the local control of blood flow.

Contribution of coronary endothelial cells to cardiac adenosine production

Experiments were performed in isolated non-working guinea pig hearts perfused according to the Langendorff technique (95% O2, 5% CO2), to evaluate the relative contribution of the coronary endothelium to the formation of cardiac adenosine during hypoxia, hypercapnia, and acetylcholine infusion. For this purpose the adenine-nucleotides of the coronary endothelium were prelabeled by perfusion of isolated hearts with 3H-adenosine (10(-8) M) for 35 min. Changes in the relative specific radioactivity (RSA) of adenosine released into the coronary effluent perfusate were used to assess changes in the relative contribution of the coronary endothelium and cardiomyocytes to total cardiac adenosine release. Hypoxic perfusion (15% O2) doubled coronary flow and increased total adenosine release by about two orders of magnitude and in addition, substantially increased the release of 3H-adenosine. The RSA of adenosine, however, was consistently depressed. During hypercapnic acidosis (9% CO2) the increase in coronary flow was associated with only a small and transient rise in cardiac adenosine release, and did not influence the formation of 3H-adenosine. In the unpaced heart, acetylcholine (10(-7) and 2 X 10(-6) M) dose-dependently increased coronary flow and the release of both adenosine and 3H-adenosine. Within the first minute, the RSA of adenosine was increased, but thereafter was decreased relative to control. In the paced heart, the effects of acetylcholine (2 X 10(-6) M) were greatly attenuated. Increasing coronary flow by bradykinin and isosorbide dinitrate or decreasing heart rate by (-)N6-phenylisopropyl-adenosine did not significantly affect effluent perfusate concentration of adenosine or its RSA.(ABSTRACT TRUNCATED AT 250 WORDS)