Am. J. Respir. Cell Mol. Biol., Vol 15, No. 4, Oct 1996, 467-472.
Early regulatory changes in rat pulmonary artery of renin-dependent systemic hypertension models
MM Itani, MG Talerico, PA Pino and T Burke-Wolin
Division of Pulmonary Medicine, New York Medical College, Valhalla 10595, USA.
Patients with systemic hypertension of various etiologies maintain their
pulmonary artery pressures within normal limits. We have reported in
isolated perfused rat lungs that low basal tone appears to be regulated by
nitric oxide (NO)-dependent and -independent mechanisms of soluble
guanylate cyclase activation, and similar results are seen in isolated
small pulmonary arteries (PA) from these animals. The abdominal aorta of
rats was ligated above the left and below the right renal artery (aortic
coarctation, AC). The mean arterial pressure (MAP) and pulmonary artery
pressure (PAP) of 24-h post-AC rats (MAP 123 +/- 7.1 mm Hg and PAP 4.2 +/-
0.9 mm Hg) showed no significant change when compared with those of sham
control rats (MAP 116 +/- 7.0 mm Hg and PAP 5.0 +/- 0.04 mm Hg). Hypoxic
contractions in isolated small rat PA (160 to 260 microns diameter) were
significantly increased from 56.7 +/- 12.0 mg in the control group to 139
+/- 31 mg in the 24-h post-AC rats (P < 0.05). PA contractions in the
presence of 100 microM nitro-L- arginine (NLA) increased from 102 +/- 34 mg
among the sham control group to 261 +/- 30 mg among the 24-h post AC rats
(P < 0.05). After NLA, the hypoxic contractions decreased to 15 +/- 2.9
mg in the control rats and 45 +/- 16 mg in the 24-h post-AC rats when
compared with pre- NLA values (P < 0.05). Western and Northern blotting
of protein and messenger ribonucleic acid (mRNA) extracted from the whole
rat lung showed a significant rise in endothelial cell nitric oxide
synthase (EcNOS; 207 +/- 34%) and EcNOS mRNA (2-fold) when comparing
controls with 24-h post-AC rats. These data indicate that there is
increased EcNOS activity and synthesis that maintain low PA tone in these
rat models as early as 24 h after AC; in addition, this effect is
independent of the systemic blood pressure.