Stereological analysis of pulmonary vasculature. Typical images of intra-acinar blood vessels in (A) control and (B) hypoxic lungs. All images are taken from semi-thin (1-2 μm) sections, are stained with Toluidine Blue and were taken with an x40 objective. Intra-acinar blood vessels in normoxic lungs were typically thin walled and had little if any medial layer and an internal elastic lamina only. Intra-acinar blood vessels from hypoxic lungs showed classic vascular remodelling, with the appearance of an external elastic lamina and medial hypertrophy. The scale bar represents 55 μm. (C) Mean wall thickness (μm) of intra-acinar blood vessels (±SEM) following 21 days exposure to control or hypoxic conditions. (D) The average length of intra-acinar blood vessel (cm) per diameter category (±SEM) following 21 days exposure to either normoxic (white circle) or hypoxic (black triangle) conditions. (E) Total intra-acinar blood vessel length was increased in the hypoxic lung, however this increase failed to reach significance (p = 0.08). (F) Mean capillary endothelium surface area (±SEM, cm2 per left lung (LL-1)) following 21 days exposure to normoxic or hypoxic conditions. * signifies significant difference from matched control (P < 0.05, ANOVA, post-hoc Student Newman Keuls test). N = 7-8 per group.