Kinetic parameters of GABA receptor binding by rat adenohypophysis membranes under conditions of modeling various levels of corticosteroids and ACGT in the body

Abstract

Kinetic parameters of l4C-GABA specific binding by rat adenohypophyseal plasma membranes were studied in experiments on modelling various corticosteroid and ACTH levels in animal body. A single hydrocortisone injection did not change Ka for high- and low-affinity GABA receptors, the number of the former (Bmax) increasing in this case. Repeated hydrocortisone injections were associated with Ko reduction for high-affinity GABA receptors and a noticeable increase of Kn for low-affinity receptors, with their number reducing. ACTH injection did not change the kinetic parameters of GABA binding with receptors. The number of high-affinity GABA receptors and their affinity reduced after removal of adrenals whereas the number of low-affinity receptors in this case was increasing. A single hydrocortisone injection to adrenalectomized rats had a normalizing effect on adenohypophyseal GABA receptors. Analysis of the results and changes in blood hormonal levels indicated that affinity changes in high-affinity receptors and changed number of low-affinity adenohypophyseal GABA receptors correlated with changes in ACTH and hydrocortisone changes.