The exPKO mice show pancreatitis-like phenotypes. (A) Real-time RT-PCR quantification of pancreatitis markers, Pap, Reg and Mac2, in exPKO showing induction in acinar cells at P16-32. Ratio of KO to WT is shown. Each value is either a single individual or average of multiple individuals. Variation among individuals is large due to differences in when these genes are induced and repressed. All genes were normalized to the levels of tubulin mRNA amplified from the same sample. Wilcoxon paired sample sign test and Fisher sign test for the combined data set of these four genes showed highly significant bias (P < 0.0001, Wilcoxon test and P < 0.001, Signs test) toward increased expression of these genes during the P16–P32 postnatal period. (B) The serum amylase level of the exPKO mice is significantly increased in the age group after P18 (*, Student's t-test, P < .01). Samples were collected from 14 and 36 exPKO animals (P14-17 and P18-25, respectively). Amylase was assayed enzymatically as described in Methods. Average fold-differences are shown (wild-type = 1.0; Error bars = s.e.m).