[Ultrastructural changes in the resorptive epithelial cells of the small intestine in rats during increased motor activity and immobilization].

Investigated were the structural changes in the epithelial resorptive cells of the duodenum and the jejunum of rats in the conditions of continuous and varying locomotor activity--intense locomotion, control, and immobilization. It was established that the microvilli in the immobilized animals were of a lower size, were irregularly distributed and lower in number. The inward bending of the lateral cell boundary was more slightly manifested. Disaggregations of the polysomes were also expressed. In rats loaded with higher locomotion activity there was more frequently a close association of the mitochondria with the granular endoplasmatic reticulum and the nucleus. The changes observed spoke of lowering of the active cell surface and lowering of the biosynthesis rate in the epithelial resorptive cells at immobilization and enhanced metabolic activity in locomotor loading.