Effects of a growth inhibitor and other factors on the tissue cathepsins of tumor-bearing rats.

It has been known from the work of Maver and Dunn (.5) and others (a review of the earlier work is given in [5]) that the presence of certain tumors causes an increased catheptic activity in various host tissues. These observations have been con firmed and extended by Zamecnik and Stephenson (10, 11), who demonstrated that only certain of the catheptic enzymes were thus affected. The ef fect of the presence of a tumor on the over-all catheptic reaction of the host tissues has again been confirmed here, and additional studies have been made concerning the effect on the cathepsins of such factors as starvation, protein depletion, and the administration of 4-dimethylaminostilbene hydrochloride, a substance indicated by Haddow, Harris, Koii, and Hoe (3) to be a potent tu mor growth inhibitor.