New method for quantitating the medial component of pulmonary arteries. Factors affecting the measurements.

The study objectives were to determine the effect of several factors related to tissue preparation on the relationship between medial area and size of the muscular pulmonary artery (defined in terms of total length of internal elastic lamina). This relationship took the form y = Axb that was linearized by plotting the square root of medial area against artery size. Complete distention of pulmonary arteries by an injection medium caused the internal elastic lamina to stretch by a factor of approximately 1.5. The relationship between medial area and artery size was unaffected by either the pressure method used for lung inflation/fixation or the tissue-embedding medium. Tissue shrinkage was considerable with paraffin embedding and negligible with glycol methacrylate. More arteries were considered measurable in glycol methacrylate-embedded tissue.