DNA polymerases in the rat pituitary gland. Effect of oestrogens and sulpiride.
Changes in the activity of DNA polymerase and [3H]thymidine incorporation into the DNA of the anterior pituitary gland were studied in oestrogenized male and pregnant rats. The activities of DNA polymerases alpha and beta, extracted in Tris--HCl or in sodium phosphate buffer were characterized according to their optimum pH and sensitivity to N-ethyl-maleimide. In the Tris-soluble fraction DNA polymerase activity is almost exclusively alpha, while in the phosphate soluble fraction it is a mixture of alpha and beta. The administration of oestrogens to male rats increases [3H]thymidine incorporation and enhances the activity of DNA polymerases in the Tris-soluble fraction, while the activity of the phosphate-soluble enzyme does not change. Sulpiride administration results in a further increment of [3H]thymidine incorporation and of DNA polymerase activity in the Tris-soluble fraction. In pregnant rats sulpiride also produces an increment of DNA polymerase activity only in the Tris-soluble fraction. Thus, the activity of the Tris-soluble fraction from APG behaves as DNA polymerase alpha. This activity changes in parallel with [3H]thymidine incorporation into DNA which is an indication of cell proliferation in the gland. This is discussed with respect to a negative feedback mechanism between intracellular prolactin concentration and DNA synthesis in the APG.
D000818:Animals; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D004967:Estrogens / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005260:Female; D008297:Male; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000201:enzymology*; D011247:Pregnancy; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D012995:Solubility; D013469:Sulpiride / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D014325:Tromethamine
D004967:Estrogens; D014325:Tromethamine; D013469:Sulpiride; D011388:Prolactin; D004259:DNA-Directed DNA Polymerase; D005033:Ethylmaleimide; D013936:Thymidine