To determine the mechanism of the glycemic response to administration of arginine in man, incorporation of arginine-U-C-14 into blood glucose was investigated in postabsorptive subjects given an intravenous infusion of 30 gm. of Larginine monochloride containing 50 μCi of L-arginine-UC-14. As expected, a prompt increase in blood glucose and serum insulin levels was observed. However, whereas the maximal increment in blood glucose of 15 to 22 mg./100 ml. occurred within twenty to thirty minutes of initiation of the infusion, recovery of arginine-C-14 in blood glucose was not detectable until after thirty to fifty minutes, reaching peak levels at 120 min. In subjects given only the tracer dose of arginine-C-14 in whom serum insulin concentration remained at postabsorptive levels, incorporation of C-14 into blood glucose was detectable within ten minutes.
It is concluded that the glycemic effect of arginine cannot be explained on the basis of gluconeogenesis from this amino acid. The insulinogenic action of arginine may contribute to the delay in incorporation of this amino acid into glucose.