Chemically, mechanically, and hyperosmolarity-induced calcium responses of rat cortical capillary endothelial cells in culture.
The purpose of the present work was to characterize calcium responses of brain-capillary endothelial cells (BCEC), the cells forming the blood-brain barrier, to chemical, hyperosmolar and mechanical stimulation. Confluent BCEC cultures were grown from capillary fragments isolated from rat cerebral cortex. Intracellular free calcium ([Ca2+]i) was measured using fura-2 and digital imaging. Our experiments show large endothelial calcium responses to substance P and ATP, up to a peak value of approximately 1000 and 600 nM, respectively, and these responses were observed in 2/3 of the cells. Calcium responses to bradykinin, histamine, and hyperosmolar sucrose or mannitol were smaller, attaining a peak in the range 180-340 nM, and were observed in a smaller fraction of the cells. No calcium responses were observed to high-potassium, L-glutamate, serotonin, carbachol, noradrenaline, and nitric-oxide donors. Consecutive superfusion of the cultures with ATP, bradykinin, and histamine showed that cells with a certain response pattern were spatially grouped; the response pattern itself varied widely between experiments. Mechanical stimulation of a single cell caused a calcium response in the stimulated cell in primary cultures and triggered an intercellularly propagating calcium wave in passaged cultures. Given the important effect of endothelial [Ca2+]i on blood-brain barrier permeability and transport, we conclude that substance P and ATP are potential modulators of blood-brain barrier function. Hyperosmolarity-induced blood-brain barrier opening is probably not mediated through endothelial [Ca2+]i.
Paemeleire
K
K
Department of Physiology and Pathophysiology, University of Ghent, Belgium.
de Hemptinne
A
A
Leybaert
L
L
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002196:Capillaries; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000098:blood supply*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D006632:Histamine / Q000494:pharmacology; D006982:Hypertonic Solutions; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013373:Substance P / Q000494:pharmacology; D013849:Thimerosal / Q000494:pharmacology
D005456:Fluorescent Dyes; D006982:Hypertonic Solutions; C049925:fura-2-am; D013849:Thimerosal; D013373:Substance P; D000001:Calcimycin; D006632:Histamine; D000255:Adenosine Triphosphate; D002217:Carbachol; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2; D009638:Norepinephrine