Observations of the fenestrated membrane of the human arterial wall.

The difference in the resistance to alkali or acid between collagenous and elastic fibers has been applied to differentiation of the two fibers. However, it is often difficult to keep the arterial elastic membrane intact and to recognize the direction of the artery correctly since the arterial tissue block has been hitherto simply scraped or teased with needles or pincettes in alkaline or acid solution. A newly devised method using heated potassium hydroxide (KOH) solution provides a simple technique for isolation of a large elastic fenestrated membrane in the muscular arterial wall. The characteristic of this method is handling of the isolated membrane in gradually diluted alkaline solutions after maceration in a strong alkaline medium. Internal elastic membrane with fenestrations has been found in all human arteries examined, although the size and form of the fenestrations have varied according to the age and arterial site. The detailed procedure and significance of this method have been discussed, suggesting its applicability to gerontological or pathological studies on the elastica of the arteries.