Basal and potassium stimulated, calcium dependent, endorphins release from pituitary cells.

Mouse pituitary tumor cells grown in tissue culture release endorphins spontaneously to the culture medium. Depolarization of these cells by incubation with high K⁺ concentration (56 mM) increased 2–3 folds the release of endorphins. The K⁺ evoked release was Ca⁺⁺ dependent by that: $\text{a}$, removal of Ca⁺⁺ ions inhibited 90% of K⁺ stimulated release. $\text{b}$, ethyleneglycol-bis (β-aminoethyl ether) N,N′-tetraacetic acid (EGTA) inhibited release of endorphins in the presence of high K⁺ and Ca⁺⁺. It is suggested that dual regulatory system inhibit and/or stimulate $\text{in-vivo}$ release of endorphins from the pituitary glands.