Intracellular calcium 'signatures' evoked by different agonists in isolated bovine aortic endothelial cells.
Agonist induced increases in intracellular free calcium, [Ca2+]i, were measured in single Fura-2 loaded bovine aortic endothelial (BAE) cells by dual wavelength microspectrofluorimetry. Low doses of ATP (less than 10 microM) induced complex changes in [Ca2+]i. These changes usually consisted of a large initial transient peak with subsequent fluctuations superimposed upon a maintained rise in [Ca2+]i. Higher doses of ATP (greater than 50 microM) produced much simpler biphasic increases in [Ca2+]i in individual cells. Acetylcholine and bradykinin also elicited increases in [Ca2+]i in single cells in confluent monolayers of endothelial cells. However, only acetylcholine produced complex fluctuations. High doses of acetylcholine evoked simple rises in [Ca2+]i similar to those seen with high doses of ATP. In contrast, bradykinin evoked relatively simple rises in [Ca2+]i at all doses used. These results indicate that the mechanisms responsible for generating agonist induced increases in [Ca2+]i in BAE cells are not homogeneous. ATP and acetylcholine produced more complex Ca2+ changes or 'signatures' in single confluent bovine aortic endothelial cells than bradykinin. All three agonists appeared to release Ca2+ from intracellular stores as well as stimulating Ca2+ influx. The possible mechanisms underlying these phenomena are discussed.
Lynch
M
M
Department of Physiological Sciences, Medical School, The University, Newcastle upon Tyne, UK.
Gillespie
J I
JI
Greenwell
J R
JR
Johnson
C
C
D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000378:metabolism; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D002417:Cattle; D004730:Endothelium, Vascular / Q000378:metabolism*; D008856:Microscopy, Fluorescence
D002120:Calcium Channel Agonists; D000255:Adenosine Triphosphate; D000109:Acetylcholine; D001920:Bradykinin; D002118:Calcium