POSTNATAL-DEVELOPMENT OF THE RAT EXOCRINE PANCREAS .2. EFFECTS OF PROTEIN-CALORIE MALNUTRITION ON AMYLASE SECRETION AND CCK RECEPTOR-BINDING

Malnutrition induces pancreatic atrophy and intracellular derangement, but its effects on cholecystokinin (CCK) receptors and the CCK-induce d secretory response remain unclear. We used a rodent model to study t he developmental effects of protein-calorie malnutrition on exocrine p ancreatic function. Simultaneous experiments evaluated postnatal alter ations in CCK-induced amylase response and receptor binding of pancrea tic acini. At all postnatal ages, somatic and pancre atic weight of th e malnourished rats was significantly below age-matched controls (p < 0.01). The malnourished rats showed a higher secretory response to CCK at 1 day of age and increased acinar sensitivity at 2 days. Maximal a mylase secretion was significantly higher at 5 and 18 days (p < 0.05), but remained similar to that of the age-matched controls at 36 days. CCK receptor binding showed no significant changes at 1 and 2 days pos tnatally in comparison with controls. At 5 and 18 days, the affinity o f the high-affinity state showed a twofold increase, while the capacit y of the high-affinity state decreased by 40-55%. At the same time, th e affinity of the low-affinity state increased significantly (p < 0.05 ), but the capacity of the low-affinity state was essentially unchange d. The acinar sensitivity of malnourished rats was consistently reduce d between 5 and 36 days, which coincided with a reduction in spare rec eptors in the malnourished rats. In conclusion, the increased amylase secretory response at 1 and 2 days of age may be due to an adaptive re sponse of endocrine function to maternal metabolic stress. The increas ed affinities of CCK receptors at 5 and 18 days may be associated with a higher secretory responsiveness, while the decreased spare receptor s may contribute to a reduction in the acinar sensitivity. These resul ts demonstrate that malnutrition induces changes in CCK binding and it s secretory response.