Vasopressin responses in electrically coupled A7r5 cells.
Changes in cytosolic Ca2+ concentration ([Ca2+]i) and in membrane potential were monitored in single A7r5 smooth-muscle cells during spontaneous spiking and after arginine vasopressin stimulation. Spontaneous Ca2+ oscillations, which were associated with the occurrence of action potentials, occurred in about 90% of the confluent monolayers investigated. This spontaneous activity was synchronized amongst all the cells of the monolayer, indicating that the cells were electrically coupled. Arginine vasopressin stimulation produced a [Ca2+]i rise that was about 5 times higher than the amplitude of the spontaneous Ca2+ oscillations and resulted in a subsequent cessation of spontaneous electrical activity and associated Ca2+ spiking, which persisted after [Ca2+]i returned to baseline. Individual cells in the monolayer responded to arginine vasopressin with a different latency. Agonist-induced Ca2+ waves within one cell propagated much more slowly than spontaneous [Ca2+]i rises. We conclude that agonist-induced [Ca2+]i increases in an electrically coupled cell monolayer can be asynchronous.
Missiaen
L
L
Laboratorium voor Fysiologie, K. U. Leuven Campus Gasthuisberg, Belgium.
Oike
M
M
Bootman
M D
MD
De Smedt
H
H
Parys
J B
JB
Casteels
R
R
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004594:Electrophysiology; D007425:Intracellular Membranes / Q000378:metabolism; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D009994:Osmolar Concentration; D051381:Rats
D001127:Arginine Vasopressin; D002118:Calcium