Metabolism of C-terminal pentapeptide of gastrin in the rat. Part III. The catabolism of the BOC-pentapeptide and its distribution in the organs.

The metabolism of labelled BOC-14 C-glycine-pentapetide was investigated in rats, both in blood and urine. We report on the following findings: --radioactivity could be measured in the blood even after the disappearance of the bioactive- and immunoreactive pentapeptide. --the bulk of the radioactivity in the blood after 8 minutes originates from a metabolite which, after subsequent systematic chemical identification, proved to be the BOC-14C-glycine fragment of the pentapeptide. --the radioactivity in the urine comes entirely from this split product of the labelled pentapeptide --the organ distribution of radioactivity of labelled pentapeptide was checked after i.v. administration; 1 minute after the injection, most of the radioactivity was found in the liver, followed by the kidney, pancreas, jejunum and lung. After 1 hour, radioactivity could be detected only in the kidneys. It was concluded that the N-terminal amino-acid of the naturally occurring pentagastrin (glycine) remains linked to the BOC protecting group in the course of the catabolism of the molecule and this fragment is excreted in the urine.