Publisher Summary This chapter presents an overview of the regulation of the mammalian corpus luteum (CL) The CL is an ovarian follicle in which the rapid regression—that is otherwise the fate of all postovulatory follicles—is temporarily arrested In the mammalian CL, progesterone secretion goes hand in hand with the postponement of regression It is fairly certain that reptilian CL also secretes progesterone The mammalian CL is formed during the period around ovulation by a transformation of the cells lining the cavity of the follicle Luteinization affects the granulosa cells in all species It involves an enormous enlargement of the cell with a great increase in the nucleus–cytoplasm ratio and the formation of a very distinct cell wall, the development of an extensive capillary network enmeshing all the cells, a marked proliferation of the endoplasmic reticulum, and its transformation from a predominantly rough to a predominantly smooth type, a marked proliferation of the mitochondria from a small round or rod shape type with lamelliform cristae into larger and more varied shapes with tubular and villiform cristae, and an increase in the complexity of the Golgi apparatus The CLs activity differs most from that of the follicle in how much rather than in what kinds of steroid it makes The principal change is a striking increase in progesterone secretion, accompanied by a variable, but severe fall or even loss of the capacity for estrogen and androgen secretion

The Regulation of the Mammalian Corpus Luteum

The concentrations of steroids in antral fluid, the number of granulosa cells, the status of the oocyte, and the diameter of each follicle were determined in human ovaries so that follicles at each stage of the menstrual cycle could be classified as large (>8 mm diameter) or small (<8 mm diameter) and healthy or atretic. The granulosa cells and thecal-enriched tissue from each follicle and the stromal tissue from each ovary were cultured for 6 days in vitro. The amounts of progesterone (P), androstenedione (Δ4), testosterone, dihydrotestosterone, es-trone, and estradiol (E2) generated by the different tissues were measured on days 0, 2, 4, and 6 of culture. It was found that granulosa cells, thecal tissue, and stromal tissue all have the biosynthetic capacity to produce (P, Δ4 (,)tes -tosterone, dihydrotestosterone, estrone, and (E2No individual steroid-secreting compartment of the ovaries studied, whether part of the follicle or of the stroma, had the exclusive capability of producing any of the above-na...

The production of progesterone, androgens, and estrogens by granulosa cells, thecal tissue, and stromal tissue from human ovaries in vitro.

Experiments were conducted in rhesus monkeys to determine whether the corpus luteum of the menstrual cycle requires pituitary gonadotropin for progesterone production and normal functional lifespan. Eight adult females were rendered anovulatory by placement of radiofrequency lesions in the arcuate region of the medial basal hypothalamus. Endogenous gonadotropin secretion and ovulatory cycles were reestablished by chronic pulsatile infusion of GnRH. Control luteal phases exhibited typical plasma progesterone patterns and ranged from 14–17 days in length. In experimental cycles, endogenous gonadotropin secretion was interrupted during the luteal phase by stopping the infusion of GnRH. When the GnRH infusion was stopped in the early luteal phase (3 days after the preovulatory estradiol peak; day 3), plasma LH fell to undetectable levels within 90 min. Plasma progesterone concentrations (1.5 ± 0.4 ng/ml) declined to undetectable levels (<0.2 ng/ml) by the afternoon of day 5 (P < 0.05). Premature menses occurr...

The Rhesus Monkey Corpus Luteum Is Dependent on Pituitary Gonadotropin Secretion throughout the Luteal Phase of the Menstrual Cycle

Human granulosa cells cultured in the presence of estradiol, FSH, and LH secreted relatively little progesterone during the first 3–5 days of culture. The cells then underwent a morphological transformation associated with a 10-fold or more increase in progestin production. Cells not cultured with the tropic hormones usually produced progestin at a lower rate. Serum was required for the expression of maximal steroidogenic activity. Inhibitors of de novo sterol synthesis, ML-236B and 5-cholesten-3β,25-diol, did not affect progestin secretion by luteinized cells cultured in 20% serum, but these inhibitors did reduce [14C]acetate incorporation into sterols by 90%. ML-236B also did not affect hCG-stimulated progesterone secretion by the cells.However, when the cells were changed into lipoprotein-deficient medium, progestin production was markedly reduced within 24 h. The addition of low density lipoproteins (LDL) to the culture fluid restored progestin production, whereas high density lipoproteins tended to f...

Progesterone Synthesis by Luteinized Human Granulosa Cells in Culture: The Role of de Novo Sterol Synthesis and Lipoprotein-Carried Sterol

In vitro evaluation of corpus luteum function of cycling and pregnant rhesus monkeys: progesterone production by dispersed luteal cells

Progesterone synthesis in vitro and the influence of exogenous gonadotropin were studied in slices of 50 individual human corpora lutea removed at different times during the reproductive cycle. Radioactive progesterone synthesis (dpm) was assessed by incorporation of radioactivity from acetate-1-14C. The progesterone contained in corpora lutea and formed in vitro from endogenous precursors (μg) was measured spectrophotometrically by its absorption of ultraviolet light. All luteal phase corpora lutea synthesized progesterone in vitro as measured by these 2 parameters (dpm and μg). No radioactive progesterone synthesis (dpm) from acetate-1-l4C was found in 3 corpora lutea obtained after onset of menses, although 2 of the 3 specimens synthesized progesterone (μg) from endogenous precursors. Corpora lutea from all phases of pregnancy and up to 4 days post partum synthesized progesterone in vitro. The capacity for steroid biosynthesis during the post-par turn period appeared to decline gradually when ...

William J. Le Maire

Papers

Steroid Hormone Formation in the Human Ovary: V. Synthesis of Progesterone in Vitro in Corpora Lute a During the Reproductive Cycle