REGIONAL VARIABILITY IN PREPROENDOTHELIN-1 GENE-EXPRESSION IN SHEEP PULMONARY-ARTERY AND LUNG DURING THE ONSET OF AIR-INDUCED CHRONIC PULMONARY-HYPERTENSION

We investigated preproendothelin-1 (ppET-1) gene expression in the mai n and midregion pulmonary artery, and peripheral lung from control she ep and from animals during the development of the structural and funct ional changes of air-induced chronic pulmonary hypertension (CPH). Mea surement of ET-1 in lung lymph (n = 7) at 1, 4, 8, and 12 d of continu ous air embolization (CAE) showed a significant increase from day 4 co mpared with controls (n = 4). A semiquantitative reverse transcription PCR for ppET-1 gene expression was developed using ovine-specific pri mers, Control sheep showed strikingly fewer ppET-1 transcripts in the midregion (22.9+/-2.3 ng cDNA equivalents) than in the main pulmonary artery and lung (736.0+/-263.7 and 705.5+/-125.7, respectively). Smoot h muscle cells (SMC) isolated from the main and midregion artery of co ntrol sheep confirmed these findings and showed higher levels of intra cellular ET-1 synthesis in the main versus the midregion artery. Diffe rences in gene expression persisted during CAE, In main pulmonary arte ry and lung, ppET-1 transcripts fell to < 1% of controls, However, tra nscripts in the midregion artery showed a gradual increase, Coincubati on of SMC from the midregion with ET-1 plus TGF-beta resulted in an in crease in intracellular big ET-1 and a decrease in SMC from the main a rtery. We conclude that SMC from the main and midregion pulmonary arte ry are phenotypically different and suggest that local synthesis of ET -1 and TGF-beta, and increased levels of ET-1 in lung lymph, regulate ppET-1 gene expression and synthesis in arterial SMC during the develo pment of air-induced CPH.