Hypoxic effects on the expression of mineralocorticoid and glucocorticoid receptors in human renal cortex epithelial cells.

The effects of both mild and severe hypoxic conditions on the expression of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) in the primary human renal cortex epithelial cells (RCEC) were investigated. Slot blot analyses were performed with human beta-actin cDNA and the cDNA probes for unique regions of MR and GR. The steady-state mRNA level of the house-keeping beta-actin gene remains the same in RCEC under either normoxic or hypoxic conditions. However, there was a 45% reduction in MR expression and a 30% increase in GR expression, under mild hypoxic condition (15% O2) over 3 days. Furthermore, cells subjected to a severe hypoxic condition (0.5% O2) for 24 hours exerted a 22% reduction in MR expression and a 64% increase in GR expression. Changes in MR and GR expression may, in part, explain the physiological changes in adrenal cortical function observed in hypoxic conditions.

Activin and inhibin have opposite effects on steroid 5 alpha-reductase activity in genital skin fibroblasts.

The transforming growth factor beta (TGF-beta) superfamily includes several closely related peptides including the activins and inhibins. Since we recently reported that TGF-beta 1 and beta 2 are potent inducers of steroid 5 alpha-reductase (5 alpha R), we have now studied the effects of these other peptides using primary cultures of human scrotal skin fibroblasts. Recombinant human activin A or inhibin A were added to cultured cells (2 x 10(5) cells) for 2 days in a serum free media and 5 alpha R activity was measured by the %-conversion of tracer [3H]-testosterone to dihydrotestosterone (DHT) over a 4-h period. Activin significantly stimulated 5 alpha R activity in a dose related manner (control 3.0 +/- 0.4%, activin (1.2 x 10(-9) M) 6 +/- 0.7%, P < 0.01, (2.4 x 10(-9) M) 8.5 +/- 0.6%, P < 0.001). In comparison, androgen (DHT 10(-7) M) induction of 5 alpha R was 4.7 +/- 0.2%, P < 0.05. Combined exposure of fibroblasts to activin (1.2 x 10(-9) M) and androgen (10(-7) M) did not result in additive or synergistic effect on 5 alpha R activity. In contrast, exposure of cells to an androgen (10(-7) M) and TGF-beta (2 x 10(-10) M) led to synergistic effects on 5 alpha R activity (control 1.5 +/- 0.1%, DHT 2.6 +/- 0.2% TGF-beta 1 4.8 +/- 0.5, TGF-beta 1 + DHT 9.2 +/- 1.2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of transforming growth factor beta and epidermal growth factor on steroid 5 alpha-reductase activity in genital skin fibroblasts.

Regulation of steroid 5 alpha-reductase (5 alpha R) activity and dihydrotestosterone (DHT) formation is central to prostate and sexual skin (hair) growth and cell function. Transforming growth factor-beta 1 (TGF-beta 1) is a ubiquitous peptide present in skin and scrotal tissue and its receptor is universally expressed. We have explored the role of TGF-beta 1 and -beta 2 on androgen formation in skin. Rat or human sexual skin fibroblasts were grown in primary cultures (passage 3-7). 5 alpha-Reductase activity was measured by the %-conversion of tracer 3H-testosterone to dihydrotestosterone over a 4 h period. Incubation of scrotal fibroblasts (2 x 10(5) cells) in serum and growth factor free media with androgen, such as DHT for two days significantly stimulates 5 alpha R in these cells (1.6-fold, p < 0.05 vs control). TGF-beta 1 alone at picomolar concentrations (2 x 10(-11) M to 2 x 10(-10) M) was a potent inducer of 5 alpha R activity in both rat (1.8-fold and 2.8-fold, respectively, p < 0.001 vs control at both doses) and human cells (TGF-beta 1 2 x 10(-10) M 3.3-fold, p < 0.001 vs control). Combined exposure of these fibroblasts to TGF-beta 1 (2 x 10(-10) M) and androgen (10(-7) M) further potentiated 5 alpha R activity (rat cells 6.5-fold, human cells 6.4-fold, p < 0.001 vs DHT or TGF-beta 1 alone).(ABSTRACT TRUNCATED AT 250 WORDS)