5-HYDROXYTRYPTAMINE STIMULATES CA-45(2+) UPTAKE BY HUMAN UMBILICAL VEIN ENDOTHELIAL-CELLS IN CULTURE - MEDIATION BY 5-HT(2) RECEPTOR SUBTYPES

In cultured human umbilical vein endothelial cells, 5-HT and alpha-methyl 5-HT stimulated [Ca-45(2+)] uptake in concentration-dependent manner, whereas the 5-HT1 agonists, m-CPP (1-(3-chlorophenyl)piperazine and 2-MPP (1-(2-methoxyphenyl)piperazine), were without effect. In turn, 5-HT-stimulated [Ca-45(2+)] uptake was inhibited in concentration-dependent manners by the 5-HT receptor antagonists ketanserin (5-HT2), LY 53,857 (5-HT2) and methiothepine (5-HT1/2) and to a lesser degeree by MDL 72222 (5-HT3) and BRL 43694 (5-HT3) whereas (+/-)-propranolol (5-HT1) was without effect. These data indicate that 5-HT stimulates Ca2+ uptake by endothelial cells via activation of a 5-HT2 receptor subtype. 5-HT was without effect on de novo prostacyclin (PGI2) synthesis over the concentration of 5-HT that elicited [Ca-45(2+)] uptake. Since 5-HT did not stimulate PGI2, an event associated with an increase in levels of intracellular Ca2+, it is postulated that the uptake of Ca-45(2+) reflects changes of Ca2+ at the level of the plasma membrane rather than on intracellular changes. 5-HT-stimulated Ca2+ uptake may be of relevance to endothelium-dependent relaxation, vascular permeability and endothelial repair and proliferation.