P. Lebrun et al., SIMULTANEOUS MEASUREMENT OF CA-45 OUTFLOW AND HUMAN PLACENTAL-LACTOGEN RELEASE FROM PLACENTAL EXPLANTS, Cell calcium, 17(5), 1995, pp. 384-392
Kinetics of Ca-45 outflow and human placental lactogen (hPL) release w
ere characterized in human placental explants. Measurements of the rat
e of Ca-45 and [H-3]-sucrose (extracellular space marker) outflow from
preloaded explants showed that, after a 40 min washout period, the Ca
-45 effluent radioactivity presumably originated from an intracellular
compartment. This view was further supported by the La3+ and temperat
ure sensitivity of the Ca-45 outflow. Moreover, the addition of ionomy
cin as well as an increase in the extracellular Ca2+ or Ba2+ concentra
tion provoked a dose-dependent rise in both the Ca-45 outflow and hPL
release. There were no systematic temporal analogies between the patte
rn of Ca-45 outflow and hPL release. Taken together, these observation
s suggest that the stimulation of Ca-45 outflow reflects an increased
rate of Ca-40 entry. The present data also extend previous observation
s indicating that hPL release can be stimulated by Ca2+ entry, Lastly,
the 'in vitro' method described herein allows one to compare rapid ch
anges in hPL release with associated ionic events and can be used to f
urther document the relationships between placental secretory response
s and cell calcium metabolism.