The 510 bp rat elastase 1 enhancer/promoter (Cela1) was used to drive expression of a rat pancreatic secretory trypsin inhibitor minigene (Spink3) containing all four exons and 2 kb of 3' flanking DNA. The three entrons were all shortened for ease in handling. Two of the four founders identified were used to extablish lines of transgenic mice. (J:96743)