Effect of ionic environment on the release of human placental lactogen in vitro.
Short-term incubation of human placental tissue in Krebs-Ringer bicarbonate buffered media with various concentrations of K+ and Ca2+ showed a graded response in human placental lactogen (HPL) release at different Ca2+ concentrations, but no effect at increased K+ concentration. Media with high Ca2+ caused an inhibition of release, while Ca2+-free media caused a stimulation in HPL release. High concentrations of Mg2+ inhibited release minimally, while Ba2+ had no effect. There was no change in HPL release of HPL but the significance of this effect is unknown. These results suggest that Ca2+ is not required for HPL secretion from placental tissue. It seems that HPL secretion in vitro does not follow the usual pattern where a physiological stimulus or high K+ concentration causes inward movement of calcium which couples stimulation to secretion.
D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007477:Ions / Q000494:pharmacology*; D007811:Lanthanum / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D010920:Placenta / Q000187:drug effects / Q000378:metabolism*; D010928:Placental Lactogen / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011247:Pregnancy; D012964:Sodium / Q000494:pharmacology; D013997:Time Factors
D007477:Ions; D001464:Barium; D007811:Lanthanum; D010928:Placental Lactogen; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium