Lack of an inhibitory influence of oocytes upon luteinization of porcine granulosa cells in culture

Abstract

Nalbandov (1972) suggested that the ovum produces a "luteostatic" substance which prevents luteinization of granulosa cells. This suggestion was derived from three lines of observation: (1) surgical ovectomy in vivo induced luteinization and increased the output of progesterone into the ovarian venous blood of rabbits (El-Fouly, Cook, Nekola & Nalbandov, 1970) and pigs (Nalbandov, 1972); (2) rat granulosa cell monolayers cultured with only a few oocytes luteinized, whereas those cultured in the presence of many ova retained their granulosa cell morphology (Nekola & Nalbandov, 1971); and (3) oocytic degeneration on the 3rd day of culture of rat follicles coincided with morphological luteinization of the mural granulosa (Stoklosowa & Nalbandov, 1972).To test this hypothesis porcine granulosa cells were cultured with and without the addition of cumulus-enclosed porcine oocytes. Granulosa cells and oocytes were collected from medium and large follicles (3-12 mm) of pig ovaries removed at a local slaughterhouse. Within 20-30 min after death the ovaries were excised and placed in 0-9% (w/v) NaCl containing 100 i.u. penicillin/ml, and 100 pg streptomycin/ml and kept at room temperature until culture 3-5 h later. Details of granulosa cell and oocyte collection have been described elsewhere (Channing & Ledwitz-Rigby, 1975 ; Tsafriri & Channing, 1975a, b (Channing, 1974). The serum contained 66 pg total oestrogens/ml as measured by radio¬ immunoassay (Channing & Coudert, 1976). The progesterone content of the serum was 3-8-4-1 ng/ ml, using a modification (Channing & Coudert, 1976) of the radioimmunoassay developed by Thorneycroft & Stone (1970). Morphological luteinization and the number of cells in the cultures were assessed as described elsewhere (Channing, 1970a, b). To some of the cultures cumulusenclosed oocytes (50/culture) and/or ovine LH (NIH-LH-S19 ; 5 pg/ml) were added. Each treatment combination was tested in eight replicate cultures. At 12-h intervals the medium was changed and progesterone was determined by radioimmunoassay using an antiserum against 1 la-hydroxyprogesterone-BSA conjugate.The progesterone secretion rate by granulosa cell cultures with and without oocytes and LH during the 12 h intervals is presented in (Nicosia & Mikhail, 1975

Cumulus cells secrete a meiosi‐inducing substance by stimulation with forskolin and dibutyric cyclic adenosine monophosphate

“…The resumption of oocyte meiosis may not only depend on active stimulation. This process may also involve a removal of inhibitory signals, as previously proposed (Channing and Tsafriri, 1977;Channing et al, 1983). A change in the balance between inhibitory and stimulatory substances of the follicle fluid might be involved in the resumption of meiosis (Westergaard et al, 1984;review, Byskov, 1979).…”

Differential Regulation of Progesterone and Estradiol Production by Mouse Cumulus and Mural Granulosa Cells by a Factor(s) Secreted by the Oocyte

“…Further studies in rats found that the addition of oocytes to granulosa cell cultures prevented morphological luteinization [14] and that luteinization of rat follicles in vitro [15] or in vivo [16] coincided with degeneration of the oocyte. Others have failed to observe any inhibitory influence of oocytes upon morphological luteinization or progesterone secretion [17][18][19]. By means of a microsurgical procedure, whereby the oocyte is removed from the oocyte-cumulus cell complex, it was shown that these oocytectomized (OOX) complexes produced 29% less estradiol, but almost 40-fold more progesterone, than did intact oocyte-cumulus cell complexes [12].…”

Oocyte-secreted factros regulate granulosa cell steroidogenesis

“…Further studies in rats found that addition of oocytes to granulosa cell cultures prevented morphological luteinisation (Nekola & Nalbandov, 1971), and that luteinisation of rat follicles in vitro (Stoklosowa & Nalbandov, 1972) or in vivo (Hubbard & Erickson, 1988) coincided with degeneration of oocytes. Others have failed to observe any inhibitory influence of oocytes upon morphological luteinisation or progesterone secretion (Nicosia, 1972;Lindner et ah, 1974;Charming & Tsafriri, 1977). It should be noted, however, that the ability for the oocyte to regulate the follicular environment is not limited to mammals, as destruction of the germinal disc region of chicken ovaries prevents the preovulatory rise in progesterone and blocks ovulation (Yoshimura e t ah, 1994), and Xenopus oocytes seem to influence the steroid synthetic pattern of the surrounding follicle cells (Wallace, 1983).…”