Breeding stock-specific variation in peptidylglycine alpha-amidating monooxygenase messenger ribonucleic acid splicing in rat pituitary

Peptidylglycine alpha-amidating monooxygenase (PAM) is a bifunctional enzym e that catalyzes the carboxyl-terminal amidation of glycine-extended peptid es in a two-step reaction involving a monooxygenase and a lyase. Several fo rms of PAM messenger RNA result from alternative splicing of the single cop y PAM gene. The presence of alternately spliced exon A between the two enzy matic domains allows endoproteolytic cleavage to occur in selected tissues, generating soluble monooxygenase and membrane lyase from integral membrane PAM. While using an exon A antiserum, we made the unexpected observation t hat Charles River Sprague Dawley rats expressed for rus of PAM containing e xon A in their pituitaries, whereas Harlan Sprague Dawley rats did not. For ms of PAM containing exon A were expressed in the atrium and hypothalamus o f both types of Sprague Dawley rat, although in different proportions. PAM transmembrane domain splicing also differed between rat breeders, and full- length PAM-1 was not prevalent in the anterior pituitary of either type of rat. Despite striking differences in PAM splicing, no differences in levels of monooxygenase or lyase activity were observed in tissue or serum sample s. The splicing patterns of other alternatively spliced genes, pituitary ad enylate cyclase-activating polypeptide receptor type 1 and cardiac troponin T, did not vary with rat breeder. Strain-specific variations in the splici ng of transcripts such as PAM must be taken into account in analyzing the r esultant proteins, and knowledge of these differences should identify varia tions with functional significance.