EXPRESSION OF MESSENGER-RNA ENCODING CAMP-SPECIFIC PHOSPHODIESTERASE ISOFORMS IN RAT PAROTID-GLANDS

In previous reports, we have shown that cAMP-specific phosphodiesteras e (PDE4) is the major PDE in the rat parotid gland, and that PDE4 is a ctivated by phosphorylation. In this study, we investigated the expres sion of PDE4 isoform genes and alternative splicing variants of PDE4D in the rat parotid gland using reverse transcriptase-polymerase chain reaction (RT-PCR). PDE4A, PDE4B, PDE4C and PDE4D of PDE4 subfamily wer e expressed. PDE4D was found to be the dominant PDE4 isoform. A weak b and of PDE4C was detectable. Three alternative splicing variants (PDE4 D1, PDE4D2 and PDE4D3) derived from the rat PDE4D gene were expressed in the parotid gland. These data suggested that the intracellular cAMP level is regulated by multiple response mechanisms through the activa tions of the PDE by phosphorylation and gene expression in the rat par otid gland.