COMPARATIVE-STUDIES BETWEEN FRESHLY ISOLATED AND SPONTANEOUSLY IMMORTALIZED BOVINE GRANULOSA-CELLS - PROTEIN SECRETION, STEROID-METABOLISM,AND RESPONSIVENESS TO GROWTH-FACTORS
Aac. Lerner et al., COMPARATIVE-STUDIES BETWEEN FRESHLY ISOLATED AND SPONTANEOUSLY IMMORTALIZED BOVINE GRANULOSA-CELLS - PROTEIN SECRETION, STEROID-METABOLISM,AND RESPONSIVENESS TO GROWTH-FACTORS, Journal of cellular physiology, 164(2), 1995, pp. 395-403
A bovine granulosa cell line (BGC-1) has been obtained by spontaneous
immortalization of primary cultures. BGC-1 cells have retained some ch
aracteristics of primary cultures, such as the hormonal regulation of
fibronectin biosynthesis. In the present study we have compared BGC-1
cells and primary cultures of bovine granulosa cells in terms of prote
in secretion, steroid metabolism, and mitogenic responses to growth fa
ctors. The pattern of protein secretion in BGC-1 cells was qualitative
ly similar to that of primary cultures. The main differences were a hi
gher proportion of fibronectin and the relative amounts of several oth
er unidentified proteins. Progesterone levels in BGC-1 cultures were u
ndetectable. When BGC-1 cells and primary cultures were incubated with
[H-3]-pregnenolone, the former showed a lower conversion rate to prog
esterone. In contrast, the conversion rate of [H-3]-progesterone to 5
alpha-reduced metabolites was markedly increased in BGC-1 cells. We al
so examined the effects of epidermal growth factor (EGF), insulin like
growth factor-I (IGF-I), and transforming growth factor-beta (TGF-bet
a) on DNA synthesis under serum-free conditions. Both primary cultures
and BGC-1 cells exhibited a stimulatory response to EGF and IGF-I on
[H-3]-thymidine incorporation. Neither BGC-1 cells nor primary culture
s showed a significant response to TGF-beta when added alone. However,
in the presence of a combination of EGF and IGF-I, TGF-beta displayed
an inhibitory effect on primary cultures while it stimulated DNA synt
hesis in BGC-1 cells even further. The addition of conditioned medium
from BGC-1 cells (BGC-1-CM) stimulated DNA synthesis on primary cultur
es to a greater extent than the addition of conditioned medium from pr
imary cultures. These results suggest that BGC-1 cells may be a useful
model to study the regulation of granulosa cell function during the p
eriod previous to the preovulatory stage of follicular development. Th
e differential responses of the immortalized cells to growth regulator
s may offer some clues on the mechanisms that control cell proliferati
on in normal tissues. (C) 1995 Wiley-Liss, Inc.