Estrogen and the subcellular distribution of luteinizing hormone releasing hormone: Rate sedimentation studies

Rate sedimentation of the 900×G supernatants (S₁) of hypothalamic homogenates from untreated male rats or ovariectomized rats with or without 5 μg estradiol benzoate (EB) revealed two populations of LHRH particles: a minor, slowly sedimenting one (peak 1) and a major, more rapidly sedimenting one (peak 2). Some LHRH-containing material also sedimented to the bottom of the gradient. The ovariectomized rats displayed more heterogeneity of particulate LHRH than did the male rats. Furthermore, the administration of EB to ovariectomized rats altered the relative sedimentation pattern of LHRH. In ovariectomized rats, hypotonic shock of S₁ prior to rate sedimentation eliminated peak 2 and post-peak 2 LHRH and increased free LHRH at the top of the gradient. Peak 1 LHRH was still present and was elevated after EB treatment. Also, EB treatment lowered the free LHRH at the top of the gradient. These data demonstrate that the administration of EB to an ovariectomized rat alters the subcellular distribution of LHRH.