Thyroid hormone regulation of neurons staining for a pro-TRH-derived cryptic peptide sequence in the rat hypothalamic paraventricular nucleus.
The influence of thyroid hormones on neurons staining for a pro-TRH-derived cryptic peptide sequence in the rat hypothalamic paraventricular nucleus was assessed by using quantitative immunocytochemistry. The antiserum used for immunocytochemical studies recognized a cryptic fragment of pro-TRH located in the Phe 178-Ser 186 region of the precursor. Hypothyroid female rats obtained following 1 month administration of 6-n-propyl-2-thiouracil (PTU) as well as euthyroid animals were treated with a low (3 micrograms/kg/day) or high (67 micrograms/kg/day) dose of L-thyroxine (T4) for 4-10 days before sacrifice. All the animals received an intraventricular injection of colchicine 2 days prior to perfusion with 4% paraformaldehyde. PTU treatment induced an increase (45% over control) in the number of immunostained neurons. The administration of a low dose of T4 to hypothyroid animals slightly increased the number of staining for a pro-TRH-derived cryptic sequence neurons, while being uneffective in euthyroid rats. In hypothyroid animals, a 4-day treatment with the high dose of T4 did not produce any changes whereas the 7-day treatment reduced the number of positive cells to 42% of control. In euthyroid rats treated with the high dose of T4 for 4 and 7 days, the number of stained neurons was reduced to 60 and 37% of control, respectively. These results indicate that thyroid hormones can modify the amounts of staining for a pro-TRH-derived cryptic sequence in hypothalamic paraventricular neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
Liao
N
N
MRC Group in Molecular Endocrinology, Laval University Medical Center, Sainte-Foy, Canada.
Bulant
M
M
Nicolas
P
P
Vaudry
H
H
Pelletier
G
G
D000595:Amino Acid Sequence; D000818:Animals; D005260:Female; D007037:Hypothyroidism / Q000473:pathology; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000473:pathology; D010286:Paraventricular Hypothalamic Nucleus / Q000032:analysis / Q000166:cytology*; D011498:Protein Precursors / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000502:physiology; D013973:Thyrotropin-Releasing Hormone / Q000032:analysis*; D013974:Thyroxine / Q000494:pharmacology*; D013997:Time Factors
D011498:Protein Precursors; D013973:Thyrotropin-Releasing Hormone; D013974:Thyroxine