Ultrasonic Reduction of Mitotic Activity in Regenerating Rat Liver

Abstract

In the adult rat liver there is ordinarily little cell division, but in response to an urgent demand for cells (as occurs after partial liver removal) large numbers of cells divide. The purpose of this study was to measure levels of mitotic activity (stimulated by partial hepatectomy) after ultrasonic treatment of the intact liver. Anesthetized male Charles River rats were treated with ultrasound and their mitotic indices compared with control animals. A continuous 2-MHz 100-mW/cm2 unfocused sound beam was oriented to impinge on the liver. The transducer was placed on the abdomen for a treatment time of five minutes. Temperature rises were less than 5°C at the transducer-abdomen junction and less than 1°C in the liver. Within two hours of treatment about 70% of the liver was surgically removed. Twenty-eight to 30 hours after partial hepatectomy (the time of peak mitotic activity in control animals) the mitotic index of the regenerating liver tissue was observed. Treated animals showed a reduction in mitotic index to about one-half that for controls. Statistical analysis showed the results to be significant at the 1% level. [This work was supported in part by grants from R. J. Reynolds Industries, Inc., and the USPHS, Food and Drug Administration, Grant RL-00129.]