Assessment of the effects of age and smoking on the media of muscular pulmonary arteries.

The effects of age and smoking on the media of muscular pulmonary arteries were studied in 23 subjects without cardio-pulmonary disease. The group ranged in age from 19 to 81 years and included 12 non-smokers and 11 smokers. Twelve representative tissue blocks were taken from each subject and all cross-sectionally cut arteries were measured from histological sections using a digitizer. Medial area was measured and artery size defined as total length of internal elastic lamina. Only arteries measuring less than 1500 micron length of internal elastic lamina were studied. For all subjects, the relationship between medial area and length of internal elastic lamina was a curve, which was linearized by plotting square root of medial area against artery size. These individual linear regression equations (y = A + bx) were used to 'predict' for each subject the amount of muscle in the walls of arteries of a specific size: 500, 1000, and 1500 micron length of internal elastic lamina. Using this type of summary data it was found that neither age nor smoking affected the media. Individual (inter-subject) variation was evident in the amount of muscle present in any size of artery, particularly in the smallest arteries. In arteries measuring 500 micron length of internal elastic lamina, the amount of muscle was positively and significantly correlated with the absolute weight of the right ventricle.