Expression of the endothelin-1 gene in the rat thyroid gland and changes in its peptide and mRNA levels in goiter formation and iodide-induced involution.
Endothelin-1 (ET-1) is a major vasoconstrictor peptide, first found in endothelial cells, and later in many other tissues, including the thyroid gland. We analysed the expression of the ET-1 gene in the rat thyroid gland and changes in ET-1 mRNA and peptide levels in goiter development and involution, two circumstances characterised by vascular changes. Thyroid hyperplasia was induced in adult Wistar rats by feeding a low iodine diet (LID) supplemented with 0.25% thiouracil for 10 days, and LID alone for 2 further days (H.12 group). Involution was induced by injecting 100 micrograms iodide and refeeding a normal diet during 6 h, 12 h, and 24 h (I.6h, I.12h, I.24h groups). Rats fed a normal iodine diet were used as controls. A specific 488 bp cDNA corresponding to the known sequence of pre-pro ET-1 was found by RT-PCR from RNA extracts in all thyroid experimental groups, as well as in lung and kidney which were used as positive controls. RP-HPLC analysis showed that ET-1 immunoreactivity eluted similarly as mature ET-1. During hyperplasia, ET-1 mRNA and peptide levels were increased 3.5- and 5-fold respectively. The relative volume of the vascular bed was more than doubled. During iodide-induced involution, the glandular ET-1 mRNA level remained elevated. The concentration of ET-1 peptide increased and was significantly greater at 12 h involution than in the H.12 group. At this time, the capillary reticulum reverted to individual capillaries and the vascular bed was significantly reduced. These data demonstrate that the ET-1 gene is expressed in the rat thyroid gland and that the ET-1 mRNA and peptide levels are increased during thyroid hyperplasia and remain elevated during a phase of rapid iodide-induced involution. These data suggest that changes in ET-1 production may play a role in control of thyroid gland trophic regulation and vascularity.
Colin
I M
IM
Histology Unit, University of Louvain Medical School, Bruxelles, Belgium.
Selvais
P L
PL
Rebai
T
T
Maiter
D M
DM
Adam
E
E
vandenHove
M F
MF
Ketelslegers
J M
JM
Denef
J F
JF
D000818:Animals; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D004032:Diet; D016232:Endothelins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D006042:Goiter / Q000378:metabolism*; D007455:Iodine / Q000494:pharmacology*; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013889:Thiouracil / Q000494:pharmacology; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*
D016232:Endothelins; D012333:RNA, Messenger; D013889:Thiouracil; D007455:Iodine