Ba2+ affects growth hormone and prolactin secretion as well as cell morphology in rat anterior pituitary cultures

The effects of barium ions (Ba2+) on the release of growth hormone (GH), and prolactin (PRL) and ultrastructural changes accompanying altered hormone secretion in primary cultures of the rat anterior pituitary gland were studied in the presence or absence of calcium ions (Ca2+) in the medium. In four days old cultures previously labelled with 14C-L-leucine radiolabelled PRL release was stimulated in the presence of both Ba2+ and Ca2+, while GH release remained unchanged. In the absence of Ca2+, Ba2+ caused a more marked PRL and a significant GH release. In seven days old cultures, Ba2+ stimulated immunoreactive GH release in the presence of Ca2+ three-fold and a dramatic GH release occurred when Ca2+ was omitted from the incubation medium. Many parenchymal cells contracted profoundly in the presence of Ba2+ without Ca2+ in the incubation medium and the discharge of secretory material was frequent in a number of granular cells that did not contract. The observation on contraction suggests that Ba2+ may activate the microtubular-microfilamentous system in pituitary parenchymal cells.