Fine structural changes in pulmonary veins of chronically hypoxic mice

The pulmonary veins of male Swiss albino mice, exposed to simulated high altitude (380 mm Hg) for four weeks were studied for structural alterations. Endothelial cells contained invaginated nuclei and an accumulation of vesicles on the adluminal surfaces. In the subendothelial region, cells which contained filaments and dense bodies were noted. Increased muscular contraction, evidenced by decrease in the width of the I-band of the sarcomere, caveolae formation, sarcolemmal invaginations, and glycogen deposition were the most evident changes in the cardiac muscle layer. These alterations were interpreted as possible morphologically adaptive changes of pulmonary venous pulmonary vasoconstriction in response to increased metabolic demands as a result of changes in pulmonary hemodynamics with chronic hypoxia.