[How does thermotherapy effectively work on benign prostatic hyperplasia--an experimental study]

Isometric contractile force of rabbit prostatic tissue in response to electric field stimulation (EFS), KCl, and phenylephrine were measured at incubation temperature of 37 degrees C, before and after thermal exposure to 42 degrees C, 45 degrees C, 48 degrees C and 50 degrees C for 30 minutes. The contractile force in response to EFS decreased after thermal exposure above 45 degrees C, and the contractile force in response to KCL or phenylephrine decreased after thermal exposure above 48 degrees C. All the contractile response abolished after thermal exposure to 50 degrees C. The results indicate that the nerve is more hear-sensitive than the smooth muscle in the prostate. Histological examination revealed shrinkage of cell body and dark staining of nuclear chromatin of the smooth muscle cells after thermal exposure above 48 degrees C. The same histological change of the smooth muscle as well as degenerative change of the nerve cells was observed on the prostate 3-7 months after clinical thermotherapy. From these results, it is suggested that clinical effect of thermotherapy is brought about from both neural and muscular damage of the prostate. Since the least temperature to cause an irreversible tissue damage ranges from 48 degrees C through 50 degrees C, we believe it is ideal to heat the prostate around 50 degrees C to obtain a good clinical effect of thermotherapy on benign prostatic hyperplasia as a minimum invasive treatment.