Differential Steroidogenic Response of Subpopulations of Porcine Granulosa Cells to Insulin-Like Growth Factor-1 (IGF-1) or IGF-1 Analogs1

Abstract

Two experiments were conducted to examine responses of porcine granulosa cells to insulin-like growth factor-1 (IGF-1) or IGF-1 analogs (des [1-3] and Long R3) that have reduced affinity for IGF-binding proteins (IGFBP). Both experiments evaluated estradiol and IGFBP production by granulosa cells after separation of cells into subpopulations that maintain long-term estradiol production in vitro (tightly bound) and those that do not (weakly associated). Granulosa cells were obtained from medium-sized follicles (4-6 mm) at random stages of the estrous cycle in experiment 1 and from the 10 largest follicles per ovary at 0 or 48 h after weaning in experiment 2. Follicle diameter and follicular fluid estradiol concentrations increased with time after weaning (p < 0.05). Tightly bound cells produced more estradiol than weakly associated cells at 24-120 h of culture in experiment 1 and from 0 to 48 h in experiment 2 (p < 0.05). In tightly bound but not weakly associated cells, IGF-1 stimulated estradiol production. The IGF analogs were more potent stimulators than IGF-1 in experiment 1 (p < 0.05); and in experiment 2, this response was restricted to cells collected at 48 h after weaning. Conversely, tightly bound cells obtained at 0 h after weaning responded similarly to IGF-1 and des (1-3). During the final 48 h of culture, weakly associated cells produced greater quantities of 28-30-kDa IGFBP than did tightly bound cells in response to IGF-1 or analogs (both experiments; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Haem oxygenase augments porcine granulosa cell apoptosis in vitro

“…However, in weakly associated PGCs, the proportion of apoptotic cells dramatically increased to approximately 90% at 24 h under the same conditions. The two subpopulations of PGCs have different characteristics regarding steroid production, mitotic potential and protein content (Marrone & Crissman 1988, Howard & Ford 1994, Duda et al 1999; this is the first report of different apoptotic responses to serum starvation between the two subpopulations of PGCs.…”

“…Tightly bound PGCs originate from the mural layers that border the basement membrane of the follicles, whereas weakly associated PGCs originate from the antral layers (Howard & Ford 1994). We were able to characterize two subpopulations of PGCs by flow cytometry and dot plot analysis, comparing forward scatter and side scatter, in both freshly isolated and cultured PGCs.…”

“…Porcine granulosa cells consist of two subpopulations, tightly bound and weakly associated (Howard & Ford 1994). Tightly bound PGCs originate from the mural layers that border the basement membrane of the follicles, whereas weakly associated PGCs originate from the antral layers (Howard & Ford 1994).…”

“…Furthermore, we examined these haem oxygenases separately in two subpopulations of PGCs, weakly associated and tightly bound, which are distinguished by size and have different functional characteristics (Marrone & Crissman 1988, Howard & Ford 1994, Duda et al 1999. Subsequently, we investigated the effects of haem oxygenase substrate and haem oxygenase inhibitor on granulosa cell apoptosis, using flow cytometry to measure subdiploid DNA fluorescence, and on the expression of Fas ligand, using quantitative analysis of western blotting and flow cytometry immunocytochemistry.…”

Influence of exogenous gonadotropin-releasing hormone on ovarian function in beef cows after short- and long-term nutritionally induced anovulation1,2

“…However, IGP-l caninhibitFSH-induced estradiol production by granulosa cells of small follicles in vitro, and slightly increases estradiol from large follicles (Spicer et aI., 1993). In pigs, IGF-I stimulates estradiol production by granulosa cells in vitro (Howard and Ford, 1994), and a synchronous increase in lGF-I and estradiol occurs in preowlatory follicles (Hammond et aI., 1988).…”