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 β-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 β-EP levels in culture medium and within cells. The results indicated that AA could obviously stimulate the release of β-EP from pituitary cells at a concentration of 2×10-5mol/L, while cortisol at 10-6mol/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 β-EP.Namely,β-EP release continuously increased for a period under the action of La3+ of different doses(10-5 mol/L and 10￣(-7) mol/L).β-EP content in cells showed similar changes.These results suggest that β-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.