Pituitary binding sites for [ 3H]-labelled luteinizing hormone releasing factor (LRF)

Abstract

Normal rat anterior pituitary cells in culture possess two binding sites for [ 3H]LRF. One is a high affinity (2 × 10 −9M), low capacity site which corresponds to the half-maximal biological potency of LRF. The second site has low affinity (2 × 10 −8M) and an enormously higher capacity to bind LRF. This second site shows only partial specificity in that inactive LRF-analogues, although not TRF, compete for binding of [ 3H]LRF. The high affinity site is competible by LRF, LRF-agonists and LRF-antagonists even in the presence of an excess of an inactive LRF-analogue which saturates the low affinity binding site.