Luteinizing hormone triggers two opposite regulatory pathways through an initial common event, receptor aggregation.
LH receptor internalization was studied with an antireceptor monoclonal antibody (aLHR) which induces Leydig cells to produce testosterone. To follow receptor-mediated aLHR internalization, cells were incubated with aLHR at 10 C for 3 h to generate an aLHR complex; this was followed by a second incubation with fluorescent labeled antimouse immunoglobulin at 34 C, a temperature which allows internalization. Within 15 min at 34 C, cytoplasmic fluorescent staining was detectable; this staining was strongly visible after 60 min. At no time was nuclear staining observable. Employing such an approach, it has also been possible to follow the fate of unoccupied receptors when cells are stimulated with a submaximal dose of LH. The results show that LH interactions with 20% of its receptors produces microaggregation, patching, capping, and internalization of free receptor sites. The results further demonstrate that cells with receptors in the state of capping are less sensitive to a second LH stimulation, suggesting that in this state receptors are no longer coupled to the adenylate cyclase system.
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal; D000242:Cyclic AMP / Q000378:metabolism; D004351:Drug Resistance; D005456:Fluorescent Dyes; D007122:Immunoelectrophoresis; D007985:Leydig Cells / Q000378:metabolism; D007986:Luteinizing Hormone / Q000276:immunology / Q000502:physiology*; D008297:Male; D051379:Mice; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011974:Receptors, LH; D013696:Temperature; D013739:Testosterone / Q000096:biosynthesis; D013997:Time Factors
D000911:Antibodies, Monoclonal; D005456:Fluorescent Dyes; D011956:Receptors, Cell Surface; D011974:Receptors, LH; D013739:Testosterone; D007986:Luteinizing Hormone; D000242:Cyclic AMP; D000262:Adenylyl Cyclases