title: The effect of thyrotropin (TSH) levels on follicular cluster formation from grafted monodispersed rat thyroid cells.
abstract: The effect of experimental conditions which alter TSH levels on the number and size of the multifollicular thyroid clusters which develop from inoculated monodispersed thyroid cells was explored. Five week-old male Fischer rats were used as thyroid cell donors and recipients. The recipients were totally thyroidectomized (Tx) 1 week before thyroid cell transplantation (group A), hemithyroidectomized (hemi Tx) 1 week before transplantation (group B), or Tx 1 day before grafting (group C). Additional groups of recipients included intact animals maintained on low-iodine diet (LID) (group D), and on normal diet (ND) (group E). The FD50, the number of grafted cells required to produce at least one follicular cluster in 50% of the transplant sites, was the lowest in group A and the highest in group E. The TSH levels in the serum on the day of cell inoculation were highest in group A and lowest in group E. Large follicular clusters tended to be more frequent in groups A and C than in group B, but the data were variable; no large clusters were found in groups D or E. The TSH levels in groups A and C 28 days after cell implantation were higher than in group B. The FD50 is thus dependent on the concentration of circulating TSH for initiation of follicle formation; large follicular clusters result from continued elevation of TSH levels.
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D006984:Hypertrophy; D007454:Iodides / Q000008:administration & dosage; D008297:Male; D009929:Organ Size; D051381:Rats; D011916:Rats, Inbred F344; D013961:Thyroid Gland / Q000254:growth & development* / Q000473:pathology / Q000637:transplantation; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood / Q000502:physiology*
chemical_list: D007454:Iodides; D013972:Thyrotropin