Using a mouse Leydig tumor cell line, we explored the mechanisms involved in thyroid hormone-induced steroidogenic acute regulatory (StAR) protein gene expression, and steroidogenesis. Triiodothyronine (T3) induced a approximately 3.6-fold increase in the steady-state level of StAR mRNA which paralleled with those of the acute steroid response ( approximately 4.0-fold), as monitored by quantita...

Using a mouse Leydig tumor cell line, we explored the mechanisms involved in thyroid hormone-induced steroidogenic acute regulatory (StAR) protein gene expression, and steroidogenesis. Triiodothyronine (T3) induced a ;3.6-fold increase in the steady-state level of StAR mRNA which paralleled with those of the acute steroid response (;4.0-fold), as monitored by quantitative reverse transcriptase-...

In adrenal zona glomerulosa cells, the calcium messenger system is the major signaling mechanism activated by physiological stimulators of aldosterone production. We present here evidence for a dual site of action of the calcium signal: 1) Calcium influx into the mitochondrion is a prerequisite to the activation of steroidogenesis. This calcium entry leads to a rise in mitochondrial calcium con...

important role in the maintenance of the differentiated functions of these organs, and is essential for the expression of all steroidogenic CYPs (Parker & Schimmer, 1997). It is also required for the expression of other genes involved in steroid hormone synthesis such as steroidogenic acute regulatory protein (StAR), 3β-hydroxysteroid dehydrogenase /Δ5-Δ4 isomerase (HSD3B) and the ACTH receptor...

Cholesterol transport is essential for many physiological processes, including steroidogenesis. In steroidogenic cells hormone-induced cholesterol transport is controlled by a protein complex that includes steroidogenic acute regulatory protein (StAR). Star is expressed as 3.5-, 2.8-, and 1.6-kb transcripts that differ only in their 3'-untranslated regions. Because these transcripts share the s...

The cyclooxygenase-2 (COX2)-dependent inhibition of Leydig cell steroidogenesis has been demonstrated. To understand the mechanism for this effect of COX2, the present study examined the role of an enzyme downstream of COX2, namely thromboxane A synthase (TBXAS), in steroidogenesis. Inhibition of TBXAS activity with the inhibitor furegrelate induced a concentration-dependent increase in cAMP-in...

BACKGROUND While menopause results in the loss of cyclic steroid production, evidence exists for persistent, albeit reduced, ovarian androgen production. In order to continue to synthesize ovarian androgens, the steroidogenic enzymes necessary for androgen biosynthesis must be present. Few studies have selectively analysed some of the steroidogenic enzymes present in the post-menopausal ovary (...

An essential component of regulated steroidogenesis is the translocation of cholesterol from the cytoplasm to the inner mitochondrial membrane where the cholesterol side-chain cleavage enzyme carries out the first committed step in steroidogenesis. Recent studies showed that a 30-kDa mitochondrial phosphoprotein, designated steroidogenic acute regulatory protein (StAR), is essential for this tr...