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1. The effects of prostaglandins E2 and F2alpha on prolactin synthesis were examined in a clonal strain of rat pituitary tumour cells, and compared with those of thyroliberin. 2. The prostaglandins and thyroliberin gave a dose-related and time-dependent stimulation of prolactin synthesis. The maximal effects (about twofold increases) were observed after 54h of treatment with 25nM-prostaglandin E2 and 2.5nM-prostaglandin F2alpha. A similar stimulation of prolactin synthesis was observed after 250nM-thyroliberin. The combined treatment with prostaglandins and thyroliberin did not increase prolactin synthesis over and above that obtained with each compound alone. 3. After removal of prostaglandins E2 and F2alpha there was a complete reversal of prolactin synthesis to pre-stimulation values 18h later (t1/2less than or equal to 9h). The rapid reversible effect of prostaglandins was in contrast with that of thyroliberin, where prolactin synthesis returned to control values with a t1/2 of about 42 h. 4. Prostaglandin E2 (5mum) and thyroliberin (5mum) increased cellular concentrations of cyclic AMP eight- and four-fold respectively. Maximal effects were observed after 2-5min of incubation. The increases in cyclic AMP were biphasic; normal values were obtained 60 min after the start of incubation with prostaglandin E2 or thyroliberin. 5. The dose/response curve showed that prostaglandin E2 caused maximal increase of cyclic AMP at 50nM. Concentrations of prostagland in E2 that caused half-maximal stimulation of cyclic AMP accumulation and of prolactin synthesis were 4 and 5nM respectively. 6. Combined treatment with prostaglandin E2 and thyroliberin in concentrations that separately caused maximal cyclic AMP increases did not result in a further increase in this cyclic nucleotide. 7. These results are consistent with a role of cyclic AMP in mediating the effects or prostaglandins and thyroliberin on prolactin synthesis. However, if cyclic AMP is involved as a common intracellular mediator of prolactin synthesis, it cannot alone explain all the effects of prostaglandins and thyroliberin in this cell system.
K M Gautvik, and
M Kriz
March 1980,
Life sciences,
K M Gautvik, and
M Kriz
June 1970,
The Journal of biological chemistry,
K M Gautvik, and
M Kriz
February 1977,
The Biochemical journal,
K M Gautvik, and
M Kriz
February 1970,
Proceedings of the National Academy of Sciences of the United States of America,
K M Gautvik, and
M Kriz
September 1978,
Biology of reproduction,
K M Gautvik, and
M Kriz
November 1970,
Proceedings of the National Academy of Sciences of the United States of America,
K M Gautvik, and
M Kriz
August 1965,
Biochemical and biophysical research communications,
K M Gautvik, and
M Kriz
February 1975,
Biochimica et biophysica acta,
K M Gautvik, and
M Kriz
July 1969,
Proceedings of the National Academy of Sciences of the United States of America,
K M Gautvik, and
M Kriz
September 1983,
The Journal of biological chemistry,
