Mechanism of the augmentative effect of high polyethylene glycol (PEG) concentrations on the thyroid stimulating activity in TSAb-IgG using a porcine thyroid cell assay.
We previously demonstrated that high polyethylene glycol (PEG) concentrations (5% PEG) significantly augmented cAMP production in response to TSAb-IgG using the porcine thyroid cell (PTC) assay. The mechanism of the stimulatory effect of 5% PEG on cAMP production was examined by a two-step incubation with PTC. TSAb-IgG was preincubated with or without addition of 5% PEG in the PTC assay for 2.5 hr (1st incubation) and separated PTC was re-incubated with fresh Hank's buffer for 5 hr (2nd incubation). cAMP production in the 1st incubation medium by co-incubation of TSAb-IgG and 5% PEG for 2.5 hr was significantly increased (3.3-fold) compared to that without 5% PEG. When the cAMP content in PTC and the incubation medium were compared in the same volume of incubation medium after co-incubation of TSAb-IgG and 5% PEG for 2.5 hr, cAMP contents in PTC were about 7-fold higher than that in the incubation medium, and this ratio did not change in the incubation medium of TSAb-IgG without 5% PEG. Similar increases in cAMP contents in PTC (6.6-fold) compared to the incubation medium were also observed with bTSH, although there was no augmentative effect of 5% PEG on cAMP production by bTSH in either the incubation medium or PTC. When PTC, which had been preincubated with normal-IgG and 5% PEG in the 1st incubation, was re-incubated with TSAb-IgG in the 2nd incubation medium, cAMP production by TSAb-IgG was not stimulated by 5% PEG. The augmentative effect of 5% PEG on cAMP production by TSAb-IgG was observed whenever 5% PEG and TSAb-IgG were co-incubated in either the 1st or 2nd incubation. However, no stimulatory effect of 5% PEG on bTSH was observed. These results suggested the stimulatory effect of 5% PEG on TSAb-IgG-stimulated cAMP production may be due to the increase of binding or incorporation of TSAb-IgG into the membranes of PTC compared to TSH.
Yamashiro
K
K
Second Dept of Internal Medicine, University of Ryukyu, Nakagami, Okinawa, Japan.
Kouki
T
T
Takasu
N
N
Inui
T
T
Ochi
Y
Y
Kajita
Y
Y
Sato
Y
Y
Nagata
A
A
D000818:Animals; D001681:Biological Assay; D002417:Cattle; D000242:Cyclic AMP / Q000096:biosynthesis*; D004357:Drug Synergism; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology*; D018828:Immunoglobulins, Thyroid-Stimulating / Q000494:pharmacology*; D009994:Osmolar Concentration; D011092:Polyethylene Glycols / Q000494:pharmacology*; D013552:Swine; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*
D007074:Immunoglobulin G; D018828:Immunoglobulins, Thyroid-Stimulating; D011092:Polyethylene Glycols; D000242:Cyclic AMP