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

Abstract

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.

Mutation in the Neural Cell Adhesion Molecule Interferes with the Differentiation of Anterior Pituitary Secretory Cells

“…The latter implies the ability of AL to modulate the rate of hormone synthesis and release at the level of the individual cell, and to adjust the total number of secretory cells at the level of the gland. Indeed, it has been shown that proliferation of secretory cells together with activation of hormone synthesis and release can induce an increase in the amount of particular hormones in the circulation [1, 2, 3, 4, 5, 6]. After cessation of stimulation, redundant cells are removed by a process involving apoptosis [7, 8].…”

Relationship between Release of LH and Incorporation of Tritiated Thymidine in the Anterior Pituitary Gland of the Castrated Male Rat: Effect of LHRH and its Highly Active Analogue Buserelin

“…The stimulation of LH release produced by a single injection of LHRH or buserelin is not accompanied by parallel variation in the incorporation of ( 3 H) thymidine into the DNA of the pituitary gland in castrated male rats. It has been previously shown that castration of rats results in an increased secretion of LH and also in a stimulation of DNA synthesis and cell proliferation in LH cells (Romano et al 1984). It is possible that castration itself produces a maximal stimulation of DNA synthesis in LH cells which cannot be stimulated further.…”

“…Burdman 1984). Replacement therapy in the castrated rats with dihydrotestosterone diminishes the release of LH and the proliferation of LH cells (Romano et al 1984). A similar relationship occurs between prolactin release and DNA synthesis in lactotrophs (Lloyd, Jacobi and Meares 1978;Kalberman, Szijan and.…”

“…A detailed description of the procedure for the measurement of the incorporation of ( 3 H) thymidine has been described previously ( Romano et al 1984). Briefly, fresh tissue (8-10 mg) was incubated under 95% 0 2 : 5% C0 2 in 0,5 Medium 199 in the presence of 1 MCi ( 3 H) thymidine for 60 min at 37°C.…”

Indomethacin inhibits the effects of oestrogen in the anterior pituitary gland of the rat

“…The secretion of several pituitary hormones is accompanied by increased cell proliferation (Burdman, Calabrese & MacLeod, 1983;Jahn, Burdman & Deis, 1984;Romano, Machiavelli, Perez et al 1984). In addition to the release of prolactin, oestrogen is also required for prolactin cells to proliferate Burdman, Calabrese, Romano et al 1984).…”