ALUNG January 22/1

Mathew, Rajamma, Newton Y.-T. Fan, Ning Yuan, Praveen N. Chander, Michael H. Gewitz, and Charles T. Stier, Jr. Inhibition of NOS enhances pulmonary vascular changes in stroke-prone spontaneously hypertensive rats. Am. J. Physiol. Lung Cell. Mol. Physiol. 278: L81–L89, 2000.—To determine the effects of chronic nitric oxide (NO) blockade on the pulmonary vasculature, 58-day-old spontaneously hypertensive rats of the stroke-prone substrain (SHRSP) and Wistar-Kyoto rats (WKY) received Nv-nitro-L-arginine (L-NNA; 15 mg·kg21 ·day21 orally for 8 days). Relaxation to acetylcholine (ACh) in hilar pulmonary arteries (PAs), the ratio of right ventricular (RV) to body weight (RV/BW) to assess RV hypertrophy (RVH), and the percent medial wall thickness (WT) of resistance PAs were examined. L-NNA did not alter the PA relaxation, RV/BW, or WT in WKY. Although the PA relaxation and RV/BW in control SHRSP were comparable to those in WKY, the WT was increased (31 6 2 vs. 19 6 1%). L-NNA-treated SHRSP showed two patterns: in one group, the relaxation, RV/BW, and WT were comparable to those in the control SHRSP; in the other, impaired relaxation (36 6 7 vs. 88 6 4% for WKY) was associated with an increase in WT (37 6 1%) and RV/BW (0.76 6 0.05). Thus the abnormal pulmonary vasculature in SHRSP at ,10 wk of age is not accompanied by impaired relaxation in PAs or RVH; however, impaired relaxation is associated with increased WT and RVH.