Investigation of testosterone-mediated non-transcriptional inhibition of Ca2+ in vascular smooth muscle cells.

The aim of the present study was to observe the effect of short-term testosterone treatment on Ca2+ in vascular smooth muscle cells (VSMCs) of male rats. Cells were loaded with the Ca2+-sensitive fluorescent indicator Fura-2 and intracellular Ca2+ signals of VSMCs were measured using a Nikon TE2000-E live cell imaging workstation. The baseline level of cytosolic Ca2+ concentration ([Ca2+]i) in resting state VSMCs was ~100 nmol/l. Testosterone alone led to a slow increase in [Ca2+]i, but there was no significant difference compared with the ethanol vehicle control. When VSMCs were stimulated with a high-potassium solution (containing 42 mmol/l of K+), [Ca2+]i rose rapidly and remained at a high plateau level. Short-term treatment using physiological (40 nmol/l) or supraphysiological (4 µmol/l) levels of testosterone at either the plateau phase or the pretreatment stage could significantly inhibit the [Ca2+]i increase induced by high-potassium solutions. Testosterone coupled to bovine serum albumin also had a similar effect and repetitive testosterone interventions over a short time-frame led to inhibition. Testosterone has a non-transcriptional inhibition effect on the [Ca2+]i of VSMCs and acts with the cell membranes of VSMCs to inhibit voltage-gated Ca2+ channel-mediated Ca2+ influx, which may be one of the mechanisms underlying testosterone-mediated vasodilation.