R. Mamluk et al., Hormonal regulation of messenger ribonucleic acid expression for steroidogenic factor-1, steroidogenic acute regulatory protein, and cytochrome P450 side-chain cleavage in bovine luteal cells, BIOL REPROD, 60(3), 1999, pp. 628-634
To examine hormonal regulation of genes pertinent to luteal steroidogenesis
, bovine theca and granulosa cells derived from preovulatory follicles were
cultured with various combinations of forskolin and insulin. On Day 8 of c
ulture, progesterone production was measured, and mRNA levels of steroidoge
nic factor-1 (SF-1), cytochrome P450 side-chain cleavage enzyme (P450(scc))
, and steroidogenic acute regulatory protein (StAR) were determined by mean
s of semiquantitative reverse transcription-polymerase chain reaction. Nota
bly, the combination of forskolin plus insulin stimulated progesterone prod
uction in luteinized theca cells. This was probably a result of a synergist
ic interaction between forskolin and insulin, observed on both StAR and P45
0,,, mRNA levels. However, in luteinized granulosa cells (LGC), forskolin a
nd insulin each independently were able to up-regulate the levels of P450(s
cc) and StAR mRNA levels, respectively. Moreover, insulin alone was suffici
ent to maintain the high steady-state levels of StAR mRNA in LGC. Both insu
lin and insulin-like growth factor I enhanced StAR gene expression in LGC.
SF-1 was constitutively expressed in bovine luteal cells; its amounts did n
ot vary between the two luteal cell types or with hormonal treatments.
In summary, this study demonstrates a distinct, cell-type specific regulati
on of StAR and P450(scc) mRNA in the two bovine luteal cell types.