Quantitative ultrastructural study on the responses of microvilli along the small bowel to fasting.

Stereological methods were employed to investigate the effects of fasting on the numbers and sizes of microvilli in three regions of the rat small bowel. Duodenal, jejunal and ileal segments displayed differences in microvillous amplification factors, absolute surface areas and mean lengths but no significant differences in the mean diameters or packing densities of microvilli. Fasting had no effects on amplification factors, mean diameters or numbers. However, fasted animals possessed significantly less microvillous surface area (0.9 versus 1.2 m2) due to a reduction in total villous surface area and, probably, to decreases in the average lengths of microvilli. In no instance was any significant interaction effect demonstrable. Thus, fasting influenced all regions of the small intestine in similar fashion. The paper concludes a study into the effects of fasting on villi and microvilli along the small bowel.