Gastrin inactivation system was investigated in Wistar male rats weighing 180-300 gm. Autoradiogram after the intravenous administration of 44μCi 125I-labeled synthetic humangastrin I (
125I-SHG) showed more radioactive accumulation in the renal cortex than that inother organs at 15 minutes. Radioactivity was also measured in various organs which wereexcised at 2, 5, 15, 30 and 60 minutes, and at 3, 6 and 12 hours after the intraevnousadministration of 0.1 μCi
125I-SHG. In the 15 to 60 minute period, significantly higherradioactivity was found in the renal tissue than in other organs. These findings agreed withthe results obtained in the autoradiographic studies.
Serum and supernatant solutions of various organs which were obtained with ultracentrifugation (105×g) were incubated with SHG at 37°C for 5 to 60 minutes. Then thegastrin like activities of the incubated medium were measured by bioassay and radioimmunoassay. While the serum showed no effect on SHG activity after incubation, thesupernates from kidney, liver, small bowel, lung, muscle and glandular stomach reduced SHGactivity. After heating the supernates at 60° for 30 minutes, the degradating effect of theseon SHG disappeared. As a whole organ, the kidney was 2.3-4.8 times and the liver 1.6-2.0times as potent as the small bowels in inactivating SHG. The other organs were less potentthan the small bowel.
It is suggested that gastrin is mainly inactivated by the kidney and liver in the rat.
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