Receptor cross-talk can optimize assays for autoantibodies to the thyrotropin receptor: effect of phenylisopropyladenosine on adenosine 3',5'-monophosphate and inositol phosphate levels in rat FRTL-5 thyroid cells.
Immunoglobulins (IgG) from patients with Graves' disease increase inositol phosphate (IP) as well as cAMP production in rat thyroid FRTL-5 cells; IgGs from normal control subjects do not. Graves' IgG-and TSH-induced IP formation is inhibited by blocking TSH receptor (TSHR) antibodies from hypothyroid patients with primary myxedema, as is the cAMP response; this suggests that the Graves' IgG are acting through the TSHR to induce both the cAMP and phosphatidyl-inositol 4,5-biphosphate signal cascades in FRTL-5 thyroid cells as in cells with recombinant TSHR. Optimal conditions for measuring the Graves' IgG-induced IP increase include a NaCl-free Hanks' Balanced Salt Solution (HBSS) buffer system and a P1 purinergic receptor agonist; the action of each is additive. Optimization by NaCl-free HBSS is similar to that observed in cAMP assays and is specific for TSH or Graves' IgG; thus, NaCl-free HBSS did not affect ATP-induced, and actually inhibited norepinephrine-induced, IP production in FRTL-5 cells. The P1 purinergic receptor agonist acts via receptor cross-talk, which also allows further optimization of cAMP assays. Thus, adenosine deaminase improves Graves' IgG-induced cAMP production by removing adenosine from the medium. Although NaCl-free HBSS improved TSH- or Graves' IgG-induced IP and cAMP production in cells with recombinant TSHR; the modulatory action of phenylisopropyladenosine was lost.
Hidaka
A
A
Section on Cell Regulation, Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland 20892.
Okajima
F
F
Ban
T
T
Kosugi
S
S
Kondo
Y
Y
Kohn
L D
LD
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001323:Autoantibodies / Q000032:analysis*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D006111:Graves Disease / Q000097:blood; D007136:Immunoglobulins / Q000097:blood / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism*; D010660:Phenylisopropyladenosine / Q000494:pharmacology*; D051381:Rats; D011983:Receptors, Purinergic / Q000502:physiology*; D011989:Receptors, Thyrotropin / Q000276:immunology*; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology
D000906:Antibodies; D001323:Autoantibodies; D007136:Immunoglobulins; D007295:Inositol Phosphates; D011983:Receptors, Purinergic; D011989:Receptors, Thyrotropin; D010660:Phenylisopropyladenosine; D013972:Thyrotropin; D000242:Cyclic AMP