EFFECTS OF PROPYLTHIOURACIL (PTU) ADMINISTRATION ON THE SYNTHESIS ANDSECRETION OF THYROGLOBULIN IN THE RAT-THYROID GLAND - A QUANTITATIVE IMMUNOELECTRON MICROSCOPIC STUDY USING IMMUNOGOLD TECHNIQUE
X. Yi et al., EFFECTS OF PROPYLTHIOURACIL (PTU) ADMINISTRATION ON THE SYNTHESIS ANDSECRETION OF THYROGLOBULIN IN THE RAT-THYROID GLAND - A QUANTITATIVE IMMUNOELECTRON MICROSCOPIC STUDY USING IMMUNOGOLD TECHNIQUE, Endocrine pathology, 8(4), 1997, pp. 315-325
To clarify the effects of an antithyroid drug on the kinetics of thyro
globulin synthesis, secretion, and reabsorption in the thyroid follicl
es, propylthiouracil (PTU) was administered to rats and the thyroid gl
ands were examined by a refined post-embedding immunogold technique du
ring and after withdrawal of PTU. Seven-wk-old male Wistar rats were a
dministered with 5 mg of PTU/d through a gastric tube, and sacrificed
at 1 and 2 wk of administration and at 1, 2, and 3 d, and 1, 2, 3, and
4 wk, after discontinuation. The administration of PTU caused a remar
kable dilatation of the rER and Golgi apparatus, but these areas gradu
ally recovered after withdrawal of PTU. During the experiment, no sign
ificant change in the density of thyroglobulin (Tg) was observed excep
t for a transient increase immediately after withdrawal of PTU. The ex
pression of Tg on subapical vesicles (SV) and follicular colloid took
a relatively parallel course; Increasing during administration of PTU
and decreasing with a transient peak immediately after treatment was d
iscontinued. In contrast to the remarkable changes in the morphology o
f compartments involved in Tg synthesis, the development of colloid dr
oplets and formation of secondary lysosomes were suppressed during and
after discontinuing administration of PTU. However, the basic pattern
of the gradient of Tg density among the cellular compartments was ess
entially retained in the experimental group. Thus the present immunoel
ectron-microscopic study provided evidence that administration of PTU
stimulates the synthesis and secretion of Tg in the follicular epithel
ium in vivo, and, also, suppresses reabsorption and degradation of Tg.
Further, it was speculated that the density gradient of Tg among the
compartments involved in Tg synthesis, secretion and storage is regula
ted by an unknown constitutive mechanism and not by the thyroid-stimul
ating hormone (TSH)-TSH receptor-mediated system.