Effect of ATP and UTP on SK-1 mRNA expression in renal mesangial cells. (a) Quiescent rat mesangial cells were stimulated with vehicle (control, 2 h) or with UTP (100 μM) for the indicated time periods (in hours). (b) Cells were stimulated with either vehicle (Co) or with the indicated concentrations of ATP and UTP for 6 h. Thereafter, RNA was extracted and taken for real-time PCR using primers for rat SK-1 and 18S-RNA. The ΔΔCt values were calculated and were taken as a measure of SK-1 mRNA expression compared to 18S-RNA expression. Results are expressed as % of control values and are means with vertical lines showing s.d. (n=3), *P<0.05, #P<0.05, **P<0.01, ##P<0.01, ***P<0.001, ###P<0.001 considered statistically significant compared to the corresponding control values.