Regulation of immunoreactive β-endorphin release from rat pituitary cell culture

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Abstract
The release of immunoreactive β-endorphin from rat anterior pituitary cells in culture was studied by radioimmunoassay and gel-filtration chromatography. Two forms of immunoreactivity were detected corresponding to β-lipotrophin (β-LPH) and β-endorphin. Cells were found to release β-endorphin-like immunoreactivity (β-endorphin LIR) into the culture medium for up to 10 days with a trough in release occurring between days 2–4. The ratio of β-LPH to β-endorphin released remained constant during the course of culture. After 4 days in culture β-endorphin LIR release was constant and responsive to modulation. Incubation with lysine-vasopressin (0·1 units/ml) produced a two- to threefold increase in release and dexamethasone (10−6 mol/l) suppressed release to 33% of controls. Neither stimulation nor suppression resulted in a change in the ratio of β-LPH to β-endorphin released. Dexamethasone suppression was not overcome by removal of dexamethasone or addition of vasopressin.