Hormonal regulation of messenger ribonucleic acid encoding steroidogenic acute regulatory protein in ovine corpora lutea.

Abstract

Steroidogenic acute regulatory protein (StAR), proposed to be involved in the transport of cholesterol to the inner mitochondrial membrane, has recently been cloned from MA-10 cells. Using reverse transcription-polymerase chain reaction, we generated a complementary DNA encoding 404 base pairs of StAR from ovine luteal tissue to perform studies regarding regulation of the messenger RNA (mRNA) encoding this protein. In Exp 1, ewes were hypophysectomized (HPX) on day 5 of the estrous cycle and administered saline or physiological regimens of LH and/or GH until collection of luteal tissue on day 12 of the estrous cycle (n = 4/group). Luteal concentrations [mean +/- SEM; femtomoles per microgram poly(A)+ RNA] of mRNA encoding StAR were lower (P < 0.05) in the HPX plus saline-treated ewes (26.4 +/- 7.3) than in day 12 pituitary-intact ewes (n = 4; 77.7 +/- 9.3). Replacement of LH (59.1 +/- 13.1), GH (59.1 +/- 12.8), or LH and GH (69.9 +/- 4.5) in HPX ewes increased (P < 0.05) concentrations of mRNA encoding StAR to values not different from those in day 12 controls. In Exp 2, ewes on day 11 or 12 of the estrous cycle were injected with prostaglandin F2 alpha (PGF2 alpha) to induce luteal regression. Corpora lutea were collected 4, 12, or 24 h after injection (n = 4-5/time point) and from untreated control ewes (n = 4) or 24 h after injection of saline (n = 4). Treatment with PGF2 alpha decreased (P < 0.05) concentrations of progesterone in serum 4, 12, and 24 h after injection. Concentrations of StAR mRNA were decreased (P < 0.01) to 47%, 19%, and 8% of control values 4, 12, and 24 h after PGF2 alpha injection, respectively. In Exp 3, ewes received ovarian arterial infusions of saline, PGF2 alpha, or phorbol 12-myristate 13-acetate (PMA), and luteal tissue was collected 0 (no infusion), 4, 12, or 24 h later (n = 3-4/group). Treatment with PGF2 alpha or PMA decreased (P < 0.05) concentrations of progesterone in serum 4, 12, and 24 h postinjection. Steady state concentrations of mRNA encoding StAR (P < 0.05) were 36% and 25% of the control value 12 and 24 h after PGF2 alpha injection. Injection of PMA decreased (P < 0.05) concentrations of StAR mRNA to 75% and 50% of control values at 4 and 12 h, but concentrations of mRNA encoding StAR were not different from control values at 24 h.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth hormone and insulin-like growth factor-I action on progesterone secretion by porcine corpora lutea isolated at various periods of the luteal phase

“…The trilostane inhibitory study showed that in GH-stimulated cells trilostane decreased progesterone secretion in the same manner as under control conditions, while a 7.2-fold higher inhibition was noted in cultures supplemented with IGF-I . This is in accordance with data of Juengel et al (1994Juengel et al ( , 1995 who showed that treatment of hypophysectomised ewes with GH alone also allows circulating concentrations of progesterone and expression of mRNA encoding StAR and cholesterol side chain cleavage P450 scc to reach normal levels, however, GH does not appear to support luteal expression of mRNA encoding 3β-HSD. On the other hand, in the presented data high stimulatory effect was noted in IGF-I treated cultures (Figs 3 and 4).…”

CCAAT Enhancer-binding Protein β and GATA-4 Binding Regions within the Promoter of the Steroidogenic Acute Regulatory Protein (StAR) Gene Are Required for Transcription in Rat Ovarian Cells

“…Moreover, in adult mouse tissues, high levels of GATA-4 are observed in the ovary, testis, and heart. Interestingly, little or no GATA-4 protein was found in the cells of the mouse corpus luteum (68), which do express record levels of StAR (20,40,70,71). One way to reconcile this apparent inconstancy is provided by assuming that the role of GATA-4 during follicular phase could be fulfilled by another member of this family, like GATA-6, which is highly abundant in the corpus luteum (68).…”

Replacement of Alanine with Asparagic Acid at Position 203 in Human Steroidogenic Acute Regulatory Protein Impairs the Ability to Enhance Steroidogenesis in vitro

“…When we reported the D203A polymorphism, we speculated that the original sequence GAC at codon 203 might be an error, since all the individuals investigated had GCC encoding Ala at codon 203 and this alanine at position 203 was conserved in all animals whose StAR molecules had been characterized, including mouse, cow, sheep, and pig [1,[24][25][26]. This speculation was favored by the completion of the euchromatic sequence of the human genome, which demonstrated that codon 203 of the STAR gene is GCC [27].…”