DNA polymerases in the rat pituitary gland

Jahn, Graciela A.; Kalbermann, L. E.; Machiavelli, Gloria A.; Szijan, Irene; Burdman, J. A.

doi:10.1016/0303-7207(80)90069-6

Cited by 10 publications

(5 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Incorporation of [3H]thymidine is a valid technique for estimating DNA synthesis and cell proliferation because a close agreement is obtained between changes in the incorporation of [3H]thymidine and variations in the activity of DNA polymerase (Jahn, Kalbermann, Machiavelli, Szijan & Burdman, 1980) and the mitotic index (Lloyd, Jacobi & Meares, 1978). In the present study we have shown that the inhibition of production of prolactin by the pituitary gland in the tumour-bearing hyperprolactinaemic rat is accompanied by a marked decrease in the synthesis of pituitary DNA.…”

Section: Discussionsupporting

confidence: 51%

“…In our present study the steroid was capable of restoring prolactin production and DNA synthesis in the suppressed pituitary glands of hyperprolactinaemic tumour-bearing rats. Conversely, we previously reported that pituitary enlargement produced by chronic treatment with oestrogen was significantly reversed by the administration of bromocriptine, a dopaminergic agent (Kalbermann et al 1980). Under these circumstances, there was also a considerable decrease in DNA synthesis, activity of DNA polymerase a, and a reduction in serum prolactin levels with a concomitant accumulation of prolactin within the gland.…”

Section: Discussionmentioning

confidence: 88%

See 1 more Smart Citation

Hyperprolactinaemia and DNA synthesis in the pituitary gland of the rat

Burdman¹,

Calabrese²,

MacLeod³

1983

Journal of Endocrinology

View full text Add to dashboard Cite

Hyperprolactinaemia produced in rats by the transplanted prolactin-secreting tumours MtTW15 and 7315a significantly (P less than 0.01) inhibited by 70% the incorporation of [3H]thymidine into the pituitary DNA of the host animals. The weight and the DNA content of the glands were significantly (P less than 0.01) reduced by 30%. The administration of haloperidol, a dopamine receptor blocking agent, to the tumour-bearing rats increased the suppressed DNA replication in the anterior pituitary glands by approximately 560% in the MtTW15-bearing rat and by 100% in the 7315a-bearing animals. Furthermore, injection of drugs which stimulate prolactin release either by blocking the synthesis of dopamine (alpha-methyl-p-tyrosine) or the re-uptake of dopamine (reserpine) stimulated DNA synthesis by 800 and 100% respectively in the anterior pituitary gland of rats bearing the MtTW15 tumour. In contrast, lisuride, a dopamine agonist, significantly inhibited the incorporation of [3H]thymidine into the DNA of the pituitary gland of normal but not hyperprolactinaemic rats. Chronically administered oestrogens to hyperprolactinaemic rats increased the weight (100%). DNA content (31%), incorporation of [3H]thymidine into DNA (680%) and synthesis and release of prolactin (300%) in the pituitary gland. The incorporation of [3H]thymidine into tumour DNA was several times higher than in the pituitary gland of the host animal and was not significantly modified by any of the above treatments. Likewise the hyperprolactinaemia of the tumour-bearing rats was not significantly changed. In conclusion, we have shown that hyperprolactinaemia inhibits DNA synthesis in the anterior pituitary gland and this inhibition can be reversed completely by a dopamine receptor blocking agent and by hypothalamic dopamine depleting drugs. We propose that dopamine regulates, either directly or indirectly, DNA synthesis in the lactotrophs of the pituitary gland, which may be responsive to negative feedback mechanisms.

show abstract

Section: Discussionsupporting

confidence: 51%

Section: Discussionmentioning

confidence: 88%

Hyperprolactinaemia and DNA synthesis in the pituitary gland of the rat

Burdman¹,

Calabrese²,

MacLeod³

1983

Journal of Endocrinology

View full text Add to dashboard Cite

show abstract

“…Thus, it is accompanied by higher activity of the enzyme DNA polymerase-, which is the replicative enzyme. In several mammalian systems including the anterior pituitary gland, the activity of this enzyme changes in parallel with variations in DNA replication (Kalbermann, Szijan & Burdman, 1919a;Jahn et al 1980). On the other hand, the activity of DNA polymerase-ß, which is the reparative enzyme, did not change after castration (data not shown).…”

Section: Discussionmentioning

confidence: 98%

“…The reaction mixture was incubated at 37°C for 15 and 30 min. The reaction was stopped and the radioactivity measured as described previously (Jahn et al 1980). The DNA polymerase-activity was characterized using the specific inhibitor V-ethylmaleimide (Sigma) at the optimum pH for both the Tris-soluble and the phosphate-soluble fractions.…”

Section: Treatmentsmentioning

confidence: 99%

“…The number of mitoses/mm2 was determined in the same anterior pit¬ uitary tissue used for immunocytochemistry. Assay of DNA polymerase activity The preparation of extracts and the assay of DNA polymerase activity in the anterior pituitary gland have been described previously (Jahn, Kalbermann, Machiavelli et al 1980). Briefly, fresh tissue (35^15 mg) was homogenized in 1ml lOmM-Tris buffer, pH 7-4 plus 2mM-ß-mercaptoethanol and centrifuged for 20 min at 24 I50g.…”

Section: Treatmentsmentioning

confidence: 99%

See 1 more Smart Citation

Correlation between LH secretion in castrated rats with cellular proliferation and synthesis of DNA in the anterior pituitary gland

Romano¹,

Machiavelli²,

Perez³

et al. 1984

Journal of Endocrinology

View full text Add to dashboard Cite

The relationship between the release of LH and the synthesis of DNA was studied in the anterior pituitary gland of castrated rats. Cell types were characterized immunocytochemically. Castration significantly (P less than 0.01) increased the concentration of LH in serum (1326%) and the incorporation of [3H]thymidine into pituitary DNA (72%). This was accompanied by an increment in the activity of the enzyme DNA polymerase-alpha (58%) and in the number of mitoses (from 2 +/- 0.1/mm2 in intact rats to 21 +/- 0.8/mm2 15 days after castration). Only 20% of the mitoses found in the pituitary gland of castrated rats were positively stained with the antiserum against the beta-subunit of LH. The other 80% did not stain either with LH antiserum or with antisera against the other pituitary hormones. There was a significant (P less than 0.01) increase in the number of LH cells in castrated rats (48%). All the changes produced in the anterior pituitary gland after castration were prevented by the administration of dihydrotestosterone. The results demonstrate that a stimulation of LH release is followed by an increase of DNA synthesis and cell proliferation of gonadotrophs in the anterior pituitary gland.

show abstract