Reaction of smooth muscle cells of blood vessels to an increase in functional load.

Changes in the muscle tissue of the caudal vena cava of rats and its branches after disturbance of the blood drainage were studied by the methods of isotope biochemistry, autoradiography, immunomorphology, and cytophotometry. Enlargement and polyploidy of the DNA-synthesizing muscle cells with activation of protein synthesis in them and the formation of intimal layers resembling the muscular layers were found in the main trunk of the vein which was dilated the most. Activation of DNA and protein synthesis in the less distended femoral vein was much less marked than in the main trunk. Activation of protein synthesis occurred after a delay compared with the activation of DNA synthesis but both processes were phases of development of hypertrophy of the muscle tissue of the vessel wall in response to increased functional loading.