Hormonal regulation of DNA polymerase-beta activity in the rat thyroid gland.
Using hypophysectomized rats, it has been shown that DNA polymerase-beta activity in the adrenal gland and testis is largely influenced by pituitary trophic hormones. Sucrose gradient centrifugation of thyroid extracts revealed three peaks of DNA polymerase-beta activity sedimenting at 3.3S, 7.3S and 12S. Of these, hypophysectomy induced a decrease in the 3.3S DNA polymerase-beta, whereas other molecular forms were affected only slightly. DNA polymerase-alpha and -gamma activities were unaffected by hypophysectomy. These changes in DNA polymerase-beta caused by hypophysectomy were reversed by daily i.p. injection of TSH. Furthermore, stimulation of the thyroid by excess TSH induced by the administration of 1-methyl-2-mercaptoimidazole resulted in an increase of all forms of thyroid DNA polymerase-beta. These results show that the level of DNA polymerase is relatively constant after hypophysectomy but that DNA polymerase-beta in the rat thyroid gland is also modulated by TSH mainly through the change of activity of the polymerase-beta which sediments at 3.3S.
Nagasaka
A
A
Department of Internal Medicine, Fujita-Gakuen Health University School of Medicine, Aichi, Japan.
Yoshida
S
S
Nakai
A
A
Ohyama
T
T
Iwase
K
K
Ohtani
S
S
Nakagawa
H
H
Masunaga
R
R
Kato
S
S
Kawabe
T
T
D000818:Animals; D004256:DNA Polymerase I / Q000378:metabolism*; D004257:DNA Polymerase II / Q000378:metabolism; D004258:DNA Polymerase III / Q000378:metabolism; D007016:Hypophysectomy; D008297:Male; D008713:Methimazole / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000201:enzymology*; D013972:Thyrotropin / Q000494:pharmacology*
D008713:Methimazole; D013972:Thyrotropin; D004256:DNA Polymerase I; D004257:DNA Polymerase II; D004258:DNA Polymerase III