Caerulein stimulates pancreatic secretory response in conscious newborn rats

The aim of our study was to measure age-dependent, caerulein-stimulated pancreatic enzyme secretion of conscious CFY suckling rats without pancreatic duct cannulation. Pancreatic secretory response was expressed as the decrease in specific enzyme (trypsin, amylase) activity compared to saline-injected control. The study was performed in three phases. In 10-d-old conscious newborn rats, single 1 and 3 micrograms/kg sc doses of caerulein induced significant decreases in specific trypsin (42 and 47%) and amylase (34 and 33%) activity 15 min after the caerulein injection; the same doses injected at 0 and 30 min evoked a similar decrease 90 min after the first injection. The 0.5 microgram/kg dose was ineffective. In 10-d-old anesthetized rats, the 90-min-decrease in total pancreatic trypsin activity, induced by graded doses (1,3,10, and 30 micrograms/kg) of caerulein, was compared to the 90-min output of trypsin in their bile-pancreatic juice. Each of the applied doses induced significant change in the total trypsin activity both in the pancreas (-33-57%) and juice (+21 +/- 49%) and its decrease in the gland corresponded quantitatively well (r = 0.52; p less than 0.01) to the increase in the simultaneous 90-min trypsin output. The age- and dose-dependent pancreatic response of 3-, 5-, 10-, and 20-d-old conscious rats was investigated under the effect of 1,3,10, and 30 micrograms/kg sc doses of caerulein injected at 0 and 30 min. In 3-d-old rats, the 10 and 30 micrograms/kg and in 20-d-old rats, the 1 and 3 micrograms/kg doses were effective, whereas in 5- and 10-d-old rats each caerulein dose applied evoked a significant decrease in pancreatic-specific trypsin activity.

The pancreas of newborn rats is in vivo less sensitive to caerulein between postnatal d 3 and 10 than in already weaned rats.