This study deals with the stimulatory effect of caerulein on pancreatic and somatic growth in CFY suckling rats before weaning. After birth, caerulein (0.25, 0.5, 1, 3, 10 and 30 μg/kg) was given subcutaneously (s.c.) 3 times daily for 10 days. Salinetreated newborn rats were used as control. Caerulein increased pancreatic weight and total pancreatic trypsin activity reaching the maximum at 1 μg/kg dose; higher doses did not cause higher values. On this basis 1 μg/kg caerulein was applied s.c. 3 times daily for 3, 5, 10 and 20 days. At the end of the treatment pancreatic weight, total pancreatic protein, DNA content, trypsin and amylase activity was measured. Increases in body weight due to caerulein treatment were found from 6 days of treatment. Caerulein treatment increased pancreatic weight, total pancreatic DNA and protein content, and trypsin and amylase activity when applied for 5, 10 and 20 days. Treatment for 3, 5, 10 and 20 days with caerulein preferentially increased pancreatic trypsin activity compared to amylase activity. Trypsin activity per mg DNA increased with time in each caerulein-treated group demonstrating that the effect of caerulein increases with duration of treatment. In the saline-treated control group, however, pronounced increase in pancreatic amylase activity compared to that of trypsin activity was found in the age between days 11 and 21. This may be explained by the observation that the plasma corticosterone level increased during this period of postnatal life. The effect of caerulein in promoting pancreatic and somatic growth of suckling rats before weaning may be attributed to a specific enhancing effect of the peptide on proteolytic (e.g. trypsin) enzyme production of the pancre
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