[Regulation of androgen receptor mRNA expression by testosterone in cultured vascular smooth muscle cells]

To investigate the effects of testosterone exposure on androgen receptor (AR) mRNA expression in cultured vascular smooth muscle cells (VSMCs).

VSMCs were cultured from the thoracic aorta of male SD rats using explant method. The total RNA was extracted by one-step guanidine isothiocyanate method and subjected to Northern blotting analysis for determining AR mRNA level. The effect of testosterone on the viability and growth of VSMCs were studied by means of cell counting and tritiated thymidine incorporation assay.

Testosterone treatment of the synchronized VSMCs for 24 h increased intracellular AR mRNA expression in a dose-dependent manner, with relative mRNA level of 97.67+/-7.22, 98.00+/-13.58, 143.33+/-10.99, 177.67+/-14.62 and 185.67+/-19.97 corresponding to testosterone doses of 0, 4 nmol/L, 40 nmol/L, 400 nmol/L and 4 micromol/L, respectively. Incubation of synchronized VSMCs with testosterone at a physiological level of 40 nmol/L for 24 h resulted in a mean of 30% up-regulation of AR mRNA level, compared with that of untreated cells. During AR up-regulation, testosterone had no significant effects on the cell number and DNA synthesis of VSMCs as measured by cell counting and tritiated thymidine incorporation assay.

Self-initiated up-regulation of AR mRNA expression occurs in synchronized VSMCs, which is independent of testosterone that influences apoptosis or growth rate of the cells, suggesting the involvement of AR in androgen regulational at the transcription level in VSMCs.