Hormonal modulation of structural alteration of rat ovarian luteinizing/human chorionic gonadotropin receptors.
The structure-stabilizing effect of homologous and heterogeneous desensitization and albumin on rat ovarian LH/hCG receptors was analyzed by thermal perturbation technique. HCG-induced down-regulation shifted the heat inactivation profile of hCG-binding sites to a temperature lower by about 7 degrees C (T50 values). In heterogeneous desensitization, which also involves uncoupling of receptors from adenylyl cyclase system, only follicle stimulating hormone (FSH) changed the stability of ovarian LH/hCG receptors. Stimulation of other hormonal receptors, which belong to the family of membrane spanning G protein-linked receptors, i.e. beta-adrenergic, glucagon, serotonin and prostaglandin E (PGE) had no effect on the stability of the LH/hCG receptor. Reduction of the stability of the LH/hCG receptor by about 3 degrees C after PGF2alpha injection to luteinized rats may be connected with specific process of luteolysis. On the other hand, albumin had a stabilizing effect on the receptor. The receptor destabilizing action of oleic acid incorporated into ovarian membranes along with calcium stimulation of endogenous phospholipase A (PLA) activity and reversal of these effects when BSA was used as fatty acid scavenger, may indicate that free fatty acids are responsible for the thermal instability of hCG-binding sites. Fluorescence quenching studies indicated that extraction of free fatty acids by albumin elevated the accessibility of fluorophores for acrylamide, and suggest that modificated lipid-protein interactions may affect the stability of the LH/hCG receptor structure.
Kolena
J
J
Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava. ueenkole@savba.sk
Jezová
M
M
Vranová
J
J
Scsuková
S
S
D000818:Animals; D001665:Binding Sites; D015536:Down-Regulation; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D006358:Hot Temperature; D007700:Kinetics; D010053:Ovary / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D011453:Prostaglandins / Q000494:pharmacology; D011489:Protein Denaturation; D051381:Rats; D011974:Receptors, LH / Q000737:chemistry* / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors
D005227:Fatty Acids; D011453:Prostaglandins; D011974:Receptors, LH; D012710:Serum Albumin, Bovine; D005640:Follicle Stimulating Hormone; D012964:Sodium; D010741:Phospholipases A