THE PATTERN OF THE CIRCADIAN-RHYTHM OF PANCREATIC-SECRETION IN FED PIGS

The pattern of the circadian rhythm of pancreatic secretion was studie d in four 6- to 7-wk-old intact male pigs that were kept in metabolic cages under 12 h light:12 h dark cycles and fed three times a day at 0 800, 1500, and 2200. Three 24-h collections of pancreatic juice and bl ood were begun at 0800 every 2nd day during 5 d. A biphasic pattern of the exocrine pancreas was detected. Secretions during the first phase (postprandial peak) contained large amounts of protein and enzymes, a nd secretions appeared immediately after feed ingestion. Secretions du ring the second phase (between meals) had lesser amounts (P <.001) of protein and enzymes, but were of longer duration (P <.001). The output of protein and trypsin activity were generally correlated (P <.001) w ith each other, but the correlation of either with the volume outflow were small. However, these variables were correlated (P < .01) with th e volume outflow at night during the second phase. Plasma concentratio ns of insulin and glucose increased after each meal, but the increase was significant(P <.05) only for insulin. Insulin and glucose concentr ations were correlated (P <.01) with each other after the meals at 080 0 and 1500. The results indicated a biphasic pattern of the exocrine p ancreas and a monophasic pattern of the endocrine pancreas in pigs. Th e regulation of these patterns seems to vary during the 24-h period. F urthermore, feed enhanced secretion, but it did not seem to be the onl y factor controlling the circadian pattern.