The distribution of 3H-gastrin and 14C-pentagastrin in the blood and lymph of rats.

3H-gastrin (0.83 mug/rat) or 14C-glycine-pentapeptide amide (100 mug/rat) were injected into the femoral vein in various groups of rats and radioactivity was measured in the arterial blood plasma and thoracic duct lymph in consecutive 5--10 min. periods for 60 minutes. Radioactivity excreted in the bile for 30 minutes was injected into the blood and lymph was followed for 120 minutes. It has been observed that labelled gastrin or pentagastrin activity reaches its peak in the plasma in the 5th minute after intravenous injection. Next, activity in the plasma decreased after the injection of labelled gastrin, but remained unchanged after the injection of labelled pentagastrin. In the lymph, radioactivity reached its peak value between 5--15 min. after the injection of the labelled hormones. This peak value was two- to threefold of plasma radioactivity measured at the same periods. After the intravenous injection of labelled pentagastrin radioactivity was excreted in the bile; injecting this radioactive bile into the jejunal lumen, radioactivity was reabsorbed mainly into the blood circulation.