Transforming growth factor-beta 1 production in porcine thyroid follicular cells: regulation by intrathyroidal organic iodine.
The present studies have demonstrated the production of transforming growth factor-beta 1 (TGF-beta 1) by porcine thyroid follicular cells (TFCs) maintained in vitro as subconfluent monolayers, and have confirmed a stimulatory effect of iodide on thyroidal TGF-beta 1 mRNA and peptide release. RNA extracted from TFCs maintained in the absence of iodide contained a 2.5 kb transcript which hybridized specifically with a cDNA probe for human TGF-beta 1, and which showed an approximate doubling in intensity in cells exposed to 10 mumol NaI/1. In the presence of the anti-thyroid thionamide drug methimazole (MMI; 1 mmol/l), the action of iodide on TGF-beta 1 mRNA was attenuated, although MMI alone had no effect on the control level of TGF-beta 1 mRNA. The TGF-beta 1 peptide content of TFC-conditioned media (TFC-CM) was assessed using the fetal mink lung cell line Mv1Lu, in which activated TGF-beta 1 specifically suppresses trichloroacetic acid-precipitable [methyl-3H]thymidine incorporation. Newly conditioned TFC-CM stimulated [methyl-3H]thymidine incorporation into Mv1Lu cells, but after heat treatment to inactivate growth stimulators and activate the latent TGF-beta 1 component this medium inhibited [methyl-3H]thymidine incorporation. This inhibitory effect was prevented by immunoadsorption of TFC-CM with a TGF-beta 1-neutralizing antiserum, confirming the specificity of the inhibitory response. The inhibitory activity of TFC-CM was increased when the TFCs were preincubated with 10 mumol NaI/1, and lost when TFCs were exposed to MMI. In conclusion, TFCs produce TGF-beta 1 mRNA and TGF-beta 1 peptide, which are both increased by iodide treatment in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)
Cowin
A J
AJ
Department of Medicine, University of Manchester, U.K.
Davis
J R
JR
Bidey
S P
SP
D000818:Animals; D017077:Culture Media, Conditioned; D066298:In Vitro Techniques; D007455:Iodine / Q000378:metabolism*; D008713:Methimazole / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013552:Swine; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics
D017077:Culture Media, Conditioned; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D008713:Methimazole; D007455:Iodine