Effects of a cholecystokinin-like peptide on DNA and polyamine synthesis in the rat pancreas.

The trophic effect of one or multiple subcutaneous injections of two different doses of a cholecystokinin-like peptide (CCK-LP) on the rat pancreas was evaluated by determination of ornithine decarboxylase (ODC) activity, the concentrations of the polyamines putrescine, spermidine, and spermine, and the activities of DNA polymerase and thymidine kinase, in addition to the contents of DNA, RNA, and protein. ODC activity was increased 10- to 20-fold already 2 h after a single injection of CCK-LP. The activity thereafter decreased and approached the control level after 6 to 8 h. The concentration of putrescine also showed a marked increase after a single injection, approaching maximum at 8 h. A slight increase was found for spermidine as well. DNA polymerase and thymidine kinase increased after 2 days of treatment. The DNA content was still normal at that time. The study suggests that the trophic effect of CCK is initiated very early. It shows that ODC activity and putrescine concentrations are early and sensitive determinants of the effect of CCK on the pancreas.