Long-term effect of growth promoting conditions on the exocrine pancreas of rats

Postnatal development of circulating cholecystokinin and secretin, pancreatic growth, and exocrine function in guinea pigs

Concentrations of cholecystokinin (CCK) and secretin from neonatal guinea pig plasma were evaluated in relation to pancreatic growth, and secretion from dispersed pancreatic acini. Plasma CCK was low at birth (3.1 +/- 0.8 pmol/L) but rose markedly by day 15 (11.0 +/- 0.8 pmol/L, p < 0.001). Plasma secretin was also low at birth (3.8 +/- 0.8 pmol/L) but peaked on day 4 (17.0 +/- 1.4 pmol/L, p < 0.001) and remained elevated through d 15. Adult nonfasting plasma CCK and secretin levels were 12.3 +/- 0.8 and 8.9 +/- 1.5 pmol/L, respectively. Pancreatic weight more than doubled during the first week of life, with the greatest increase during the first 4 d (156 +/- 4 to 262 +/- 10 mg/100g body wt, p < 0.001). Body weight increased most dramatically during the second week (126 +/- 9 to 190 +/- 7 g p < 0.001). Amylase secretion from isolated acini stimulated by CCK-8, carbachol, phorbol ester, forskolin, and calcium ionophore (A23187) was present at birth. The percentage of total amylase content secreted in response to CCK, carbamylcholine, and secretin did not change during the first 2 wk of neonatal life, and was independent of surges in circulating CCK and secretin. These results indicate that functional maturity of the guinea pig pancreas for amylase secretion occurs early and is different from the rat, mouse, pig, and human. Since results can readily be compared between animals of different postnatal ages, the neonatal guinea pig is ideally suited for the study of hormonal effects on acinar cell function.

The importance of the centroacinar region in cerulein-induced mouse pancreatic growth

Early proliferation events within different exocrine pancreatic cell compartments were studied in mice with or without cerulein administration. A technique with 3H-thymidine labeling of DNA-synthesizing cells was used. Groups of five animals were given either cerulein (20 micrograms/kg/24 h) or saline subcutaneously twice daily. 3H-thymidine was given as a single injection, 300 microCi intraperitoneally, on the 3rd and 8th day of cerulein or saline administration, and the fraction of labeled cells in each cell compartment (3H-thymidine labeling index, TLI) was calculated on the basis of autoradiographic analyses of the tissue. In a second set of experiments the distribution of the tracer between cell compartments, when given on the 3rd day of cerulein (saline) administration, was followed over a 5-day period. The highest proliferative rate was observed in the centroacinar cell compartment (TLI, 6%), and newly formed cells were accumulated during the 5-day 'chase' period. During the same time the relative amount of labeled centroacinar cells increased and comprised 40% of all labeled exocrine cells. The relative size of the compartment did not increase, indicating increased cell turnover with loss of or possibly migration of centroacinar cells into other pancreatic cell compartments. Weak and no trophic effects of cerulein were seen on the acinar and ductal cell populations, respectively. In the control group labeled ductal cells were significantly reduced during the chase period. This was not observed in the cerulein group, indicating addition of labeled cells to this compartment from other sources. A significant non-cerulein-dependent relative increase and decrease of the ductal and acinar cell compartments, respectively, were observed during the chase period.(ABSTRACT TRUNCATED AT 250 WORDS)