Pseudopregnancy-dependent changes in rat ovarian LH/hCG receptors in relation to membrane lipid fluidity

Abstract

Summary ―The specific binding of [!251]

Early hCG‐induced desensitization of rat ovarian LH/hCG receptors is associated with altered physical state of membranes

“…1 -~ phosphate buffer, pH 7.4. Ovarian membranes (100//g protein) were incubated at 25°C for 1 h with 2 ml of DPH in the above buffer [2,8,9]. Differential scanning calorimetry (DSC) measurements were performed on a Privalov DASM-4 adiabatic differential microcalorimeter with a scan 0.5°C/min.…”

“…RIA and protein binding methods were used for the determination of progesterone and cAMP concentration [8,9]. Cholesterol was assayed enzymatically [18].…”

“…Luteinized ovaries were produced in 26-day-old rats (Wistar strain) by sc administration of 50 IU PMSG followed 56 h later by 30 IU hCG [9]. Desensitization was induced by injecting 75 IU hCG on day 5 of pseudopregnancy; control rats received saline.…”

“…The cell membrane is a dynamic matrix which responds to various physiological conditions by changing its physical state. The ordering of the lipid environment in which the LH/hCG receptor is embedded can affect the accessibility of the receptor, as well as transmission of the signal across the membrane [8,9]. There are several reports showing that in vitro additions of insulin and growth hormone can elicit changes in the membrane lipid fluidity in adipocytes and erythrocytes [10][11][12].…”