6-ketoprostaglandin-f1-alpha and 5-carboxamidotryptamine

Vascular serotonin 5-HT1 receptors have quiescent constrictor activity that is activated by other vasoactive agents such as histamine. Previously, we observed that the 5-HT1-selective agonist 5-carboxamidotryptamine (5-CT) potentiated histamine-stimulated arachidonic acid (AA) mobilization and prostaglandin production in human aortic endothelial cells (HAEC). In the present study, 5-CT was found to potentiate histamine-stimulated calcium mobilization but had no effect on intracellular calcium when added alone. Treatment of HAEC with human low-density lipoprotein (LDL) for 20 hours inhibited the histamine- plus 5-CT-stimulated production of prostaglandin F2alpha (PGF2alpha) and the prostacyclin metabolite 6-keto-PGF1alpha. However, the effects of histamine and histamine potentiation by 5-CT on intracellular Ca mobilization and AA release were resistant to LDL treatment. Conversely, the subsequent receptor-independent conversion of AA to prostaglandins was inhibited by LDL. These results demonstrate that histamine and serotonin receptor activity, measured as the stimulation of Ca and AA mobilization, is resistant to LDL exposure under mild oxidizing conditions, whereas the receptor-independent synthesis of prostaglandins is inhibited by LDL. The results also suggest that the LDL-stimulated mobilization of cellular AA is responsible for the LDL-mediated inhibition of prostaglandin synthesis. These findings suggest a mechanism by which LDL and/or atherosclerosis could promote the vascular liberation of AA that is not converted to endothelium-derived prostaglandins and is therefore available as substrate for the production of other eicosanoids.

Topics: 6-Ketoprostaglandin F1 alpha; Aorta; Arachidonic Acid; Calcium; Cells, Cultured; Culture Media; Cyclic AMP; Dinoprost; Dose-Response Relationship, Drug; Drug Synergism; Endothelial Cells; Histamine; Humans; Lipoproteins, LDL; Receptors, Serotonin, 5-HT1; Serotonin; Time Factors

The ability of serotonin 5-HT1 receptors to increase vascular tone was previously found to be activated by vasoconstrictiors such as histamine. In this study, treatment of cultured human aortic endothelial cells (HAEC) with the 5-HT1-selective agonist 5-carboxamidotryptamine (5-CT) alone had no effect on the levels of prostaglandin F2alpha (PGF2alpha) or 6-keto-prostaglandin F1alpha (6-keto PGF1alpha). However, 5-CT potentiated the histamine and thrombin stimulated increases in prostaglandins released by HAEC. In the presence of histamine, increasing doses of 5-CT caused a steep rise in PGF2alpha levels resulting in an increase in the ratio of PGF2alpha over 6-keto PGF1alpha. The ability of 5-CT to potentiate prostaglandin production was correlated with its ability to potentiate the histamine and thrombin mediated mobilization of arachidonic acid. These results demonstrate that the ability of 5-HT1 receptors to stimulate prostaglandin production in endothelial cells is activated by histamine and thrombin.

Topics: 6-Ketoprostaglandin F1 alpha; Arachidonic Acid; Dinoprost; Dose-Response Relationship, Drug; Drug Synergism; Endothelium, Vascular; Histamine; Humans; Prostaglandins; Receptors, Serotonin; Receptors, Serotonin, 5-HT1; Serotonin; Serotonin Receptor Agonists; Thrombin