Geometric model of the rat intestinal mucosa for stereological evaluation of villus amplification factors.

This study was prompted by a desire to compare villus amplification factors at various sites along the small intestine of the laboratory rat. The paper describes a precise and efficient stereological method for achieving this objective. The method relies on conventional intersection counts performed exclusively on transverse sections. Analyses are based on six adult rats. Pieces of small bowel fixed by in situ perfusion were taken from proximal, middle and distal regions. Intersection counts on villus and primary mucosal surfaces were performed on transverse and longitudinal sections through the same regions. These counts revealed that intestinal architecture can be reasonably approximated by the simple geometric model of an isotropic villus surface on an anisotropic (cylindrical) primary mucosal surface. As a result, intersection counts may be confined to transverse sections (to reduce sampling variance) and the appropriate ratio estimator multiplied by the numerical coefficient 4/pi (to obtain an estimate of surface amplification due to villi).