The Kinetic and The Thermodynamic Studies on the Binding of 125I-Testosterone to Its Receptors in Ovarian Tumors Homogenate

Abstract

The aim of this work is to study the Kinetic and thermodynamic parameters of binding of 125I-testosterone to its receptors in ovarian tumor homogenates. It is very important to know the kinetic and thermodynamic parameters for hormones because the binding of testosterone to the its receptor initiates a signaling cascade that results in nuclear translocation of the liganded receptor and transcriptional modulation of target genes. Two groups of ovarian tumor patients were included in this study. Group I contained 33 patients with benign ovarian tumor. Group II consisted of 22 patients with ovarian cancer. Time-course of the association of 125I-testosterone with its receptor in human ovarian tumors at four different temperatures revealed the time and temperature dependency (8hrs with 25oC for benign and 8hrs 37oC for malignant). Association kinetics indicated pseudo first order kinetics for the binding. Time-courses, Scatchard, Van't Hoffs and Arrhenius plots led to the theoretical determination of thermodynamic parameters of both the standard state (i.e., H, G, S) and transition state (i.e., H*, G*, S*)