Elemental maps in human allantochorial placental vessels cells. 3. 5-hydroxytryptamine effects.
The membrane potential, a regulator of vascular tone, is a function of the physiological activities of ionic channels (particularly, K+ and Ca2+ channels in these cells). These channels regulate the ionic distribution into these cells. Micro-particule induced X-ray emission (PIXE) analysis was applied to determine the ionic composition of vascular smooth muscle cells (VSMCs) and of vascular endothelial cells (VECs) in the placental human allantochorial vessels in a physiological medium (Hanks'solution) modified by the addition of a chemical stimulus: 5-hydroxytryptamine (5-HT), an activator of the voltage-sensitive Ca2+ channels. In VSMCs (media layer), the addition of 5-HT induced no modification of the Na, K, Cl, P, S and Ca concentrations but increased Mg concentration. In endothelium (VECs) 5-HT addition implicated an increase of the K, S, Ca concentrations, the concentration of the other ions remained constant. In VECs, Ca and K increase is due to open of L-type voltage-dependent Ca2+ channels and of K(Ca) channels. 5-HT induces also a secretion of endothelium hyperpolarizing factors which implicate decrease of [Ca2+]i in VSMCs opposite to a direct increase by 5-HT. Increase in [Mg2+]i may be due to activation of the Ca/Mg exchanger.
Guiet-Bara
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A
Laboratoire de Physiologie et Physiopathologie, Université P. et M. Curie, Bât. A, 4 Place Jussieu, 75252 Paris Cedex 05, France.
Michelet-Habchi
C
C
Barberet
Ph
P
Dutta
R K
RK
Moretto
Ph
P
Bara
M
M
D000482:Allantois / Q000098:blood supply; D001808:Blood Vessels / Q000378:metabolism*; D002823:Chorion / Q000098:blood supply; D004730:Endothelium, Vascular / Q000378:metabolism; D006801:Humans; D007477:Ions / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D010920:Placenta / Q000098:blood supply / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism*
D007477:Ions; D012701:Serotonin