Figure 3. Messenger ribonucleic acid expression of trypsinogen isoforms in the retina and pancreas. A: Messenger ribonucleic acid (mRNA) coding for trypsinogen-2, -3, and -4 was found in all retinas with reverse transcriptase polymerase chain reaction (RT–PCR). No trypsinogen-1 coding mRNA was found in any retina. B: Testing of the primers on pancreas complementary deoxynucleic acid (cDNA), which served as positive control, showed that all primers produced products of correct size (A and B). The housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as a control to confirm the presence of RNA in the samples. The 100 bp DNA marker is shown on the right side of the gels.