Estradiol stimulation of LH response to LHRH and LHRH binding in pituitary cultures

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Abstract
The relationship between 17 beta-estradiol (E2) stimulation of luteinizing hormone (LH) response to LH-releasing hormone (LHRH) and E2 effect on LHRH binding was examined in pituitary monolayer cultures prepared from female rats. E2 pretreatment significantly (P less than 0.05) augmented the LHRH-induced LH release to 158-180% of the non-E2-treated controls. The maximal E2-priming effect could be observed after 1 day of treatment. E2 treatment for 3 days stimulated [D-Ala6]luteinizing hormone-releasing hormone (LHRHa) binding to about 1.5-fold that of the non-E2-treated controls without affecting the dissociation constant of LHRH receptor (Kd = 4 X 10(-10) M). The stimulatory effect of E2 on cell proliferation as determined by [3H]thymidine incorporation was also observed 3 days after treatment. However, E2 stimulation of LH accumulation in the cultured cells could be detected as early as 4 h after treatment. These results indicate that E2-priming effect on pituitary LH response to LHRH is initially associated with an increase in cellular LH content and later associated with increases in LHRH binding and in an index of cell proliferation that may include the LH-producing cells.