Modulation of thyroidal radioiodine uptake by theophylline.
Diagnostic and therapeutic use of radioiodine in the management of thyroid disorders depends on the ability of thyroid cells to concentrate radioiodine, a process regulated by thyrotropin and dependent on the intracellular increase in cAMP. We tested the ability of theophylline, a drug known to increase intracellular cAMP via inhibition of phosphodiesterase, to modulate the thyroidal radioiodine uptake in FRTL-5 cells, in mice and in humans. In FRTL-5 cells, theophylline increased the uptake of radioactive iodine and intracellular cAMP only at low concentrations (1 microM). In mice, theophylline increased slightly the radioiodine uptake, although this increase varied from 1.5- to 6.6-fold. In humans, theophylline decreased slightly the radioiodine uptake, a decrease that became more pronounced with time after radioiodine administration. These studies suggest that theophylline modulates the radioiodine uptake in a dose-dependent fashion, although the modulation is mild and probably not applicable to the clinical setting.
Lee
J M
JM
Department of Pathology, The Hopkins Medical Institutions, 720 Rutland Avenue, Baltimore, MD 21205, USA.
Zemans
R L
RL
Hejazi
M
M
Chin
B B
BB
Ladenson
P W
PW
Caturegli
P
P
D000328:Adult; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D006801:Humans; D007454:Iodides / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D011877:Radionuclide Imaging; D013806:Theophylline / Q000494:pharmacology*; D013961:Thyroid Gland / Q000166:cytology / Q000000981:diagnostic imaging* / Q000378:metabolism*
D007454:Iodides; D007457:Iodine Radioisotopes; D010726:Phosphodiesterase Inhibitors; D013806:Theophylline; D000242:Cyclic AMP