The concentration of glucose, used in studies, may be another reason for the discrepant effects of NO on insulin secretion: at low glucose concentration (7 mM), L-NAME has no effect on insulin secretion in isolated islets from freely fed mice but slightly stimulates insulin secretion in islets from starved animals. At high glucose concentrations (20 mM), L-NAME potentiates insulin secretion in islets from both freely fed and fasted mice (Eckersten and Henningsson, 2012[28]). Regarding the overexpression of iNOS at high glucose concentrations, increased insulin secretion by L-NAME may be due to inhibition of iNOS. Another factor that should be taken into account is the concentrations of NOS inhibitors used in the studies. The effect of L-NAME on insulin secretion seems to be concentration-dependent, as concentrations of 0.1-5.0 mM did not significantly influence basal insulin release in mouse isolated islets while at a high concentration (10 mM), it induced a 3-fold increase in insulin secretion (Panagiotidis et al., 1995[100]).