[Effects of lanthanum ion on beta-endorphin biosynthesis and release in rat pituitary cells]

By using the primary culture method for pituitary cells in CSFM established in our laboratory, we studied the effects of lanthanum ion (La3+) on the biosynthesis and release of beta-endorphin-like immunoreactive substances in rat pituitary cells. Anterior and intermediate/posterior pituitary cells from male rats were cultured with arachidonic acid (AA), cortisol, dexamethasone (DEX) and lanthanum chloride. RIA was used to determine beta-EP levels in culture medium and within cells. The results indicated that AA could obviously stimulate the release of beta-EP from pituitary cells at a concentration of 2 x 10(-5) mol/L, while cortisol at 10(-6)mol/L and DEX at 10(-7)mol/L inhibited this release. These data coincide with results reported in the literature and thereby prove the reliability of the method used. When incubated with pituitary cells, lanthanum chloride induced a dose- and time-dependent release of beta-EP. Namely, beta-EP release continuously increased for a period under the action of La3+ of different doses (10(-5)mol/L and 10(-7)mol/L). beta-EP content in cells showed similar changes. These results suggest that beta-EP biosynthesis and release in rat anterior and intermediate/posterior pituitary cells are stimulated by lanthanum ions. They also provide experimental evidence for explaining the analgesic mechanism of lanthanum ions at the cellular level.