Tissue culture of normal rat glomeruli: contractile activity of the cultured mesangial cells.

Rat glomerular epithelial and mesangial cells, and rat skin fibroblasts, were cultured in RPMI medium containing 15% decomplemented fetal bovine serum. They were incubated for 1 h at 37 degrees C with 2 mM [Ca2+]. At that time, their response to various concentrations of angiotensin II, norepinephrine and carbamylcholine was studied by phase contrast microscopy. Only the mesangial cells exhibited contractile activity in the presence of 10(-10) M angiotensin II and 10(-6) M norepinephrine, as demonstrated by the reduction of their length or, more frequently, by modification of their shape. No contractile activity was observed in the presence of 10(-5) M carbamylcholine. The percentage of contractile cells increased proportionally to the concentration of angiotensin II, reaching about 35% with 10(-6) M angiotensin II. The contractile activity was reversible. Specific inhibitors, i.e. Sar1-ala8-angiotensin II and phenoxybenzamine, when administered in concentrations 10 to 100-fold higher than that of the corresponding agonists, completely blocked the contractile response. This competitive effect was also reversible. The data, therefore, suggest that mesangial cells in culture display some functional properties of smooth muscle cells.