Characteristics of inflammation-induced hypertrophy of rat intestinal smooth muscle cell.

Inflammation of the human intestine causes thickening of the smooth muscle layers, and studies in rats infected with Trichinella spiralis (Tsp) have shown hyperplasia of the intestinal smooth muscle cells (ISMC). We have shown that Tsp-induced inflammation caused a fivefold increase in total protein per ISMC over control, while ISMC from the noninflamed distal ileum also showed a threefold increase. The amount of alpha-smooth muscle (SM) actin per ISMC increased nearly 500% over control by postinfection (PI) day 6. The proportion of alpha-SM actin in the total cellular protein increased 200% by day 6 PI, indicating a higher density of alpha-SM actin in the hypertrophied ISMC. Gamma-SM actin mRNA increased sharply and was matched by an increased fractional content of gamma-SM actin protein. These increases in the smooth muscle-specific actins may affect force production and further demonstrate the plasticity of smooth muscle in the inflamed intestine.