Smooth muscle cell hypertrophy and hyperplasia in the partially obstructedgut of the rat: A quantitative evaluation

Partial surgical stenosis of the gut induces smooth muscle cell hypertrophy and hyperplasia in the loops upstream from the obstruction in a few days. In the present study we report a quantitative evaluation of these phenomena in the circular smooth muscle layer of the small intestine of the rat 7 da ys after a subtotal stenosis. In the loops upstream from the obstruction, l umen diameter and muscle wall thickness were found to be, increased in comp arison with downstream tracts. Morphometrical analysis showed that cross-se ctional profile areas of smooth muscle cells, within the circular layer of upstream loops, significantly increased in size. Moreover, smooth muscle un derwent a marked cell hyperplasia; in fact, estimates of the number of smoo th muscle cell nuclear profiles turned out to be from 2.0 to 3.8 times grea ter in upstream loops than in downstream loops. The relation between the de gree of lumen dilatation and the degree of the increase of the circular mus cle layer thickness and of hypertrophic and hyperplastic response is discus sed.