Time-dependent changes of plasma ribonuclease activity in female Wistar rats under combination therapy of ovarian carcinoma.

Determinations of plasma ribonuclease were recommended in 1977 by Sheid et al. for laboratory diagnosis of ovarian carcinoma. We investigated the turnover of transfer ribonucleic acid (tRNA) as the substrate of the enzyme in healthy female inbred rats under the multistep-massive dose therapy of ovarian carcinoma usual at the Department of Gynecology, University of Giessen. Whereas mitopodozide, percutaneous irradiation of the abdomen and teniposide did not have any detectable influence on the enzyme activity, the enzyme was strongly suppressed by the other therapy steps: minima of tRNA turnover were observed on the 2nd day with adriamycine, on the 4th day with methotrexate and methotrexate/folinic acid, on the 6th day with cyclophosphamide and fractionated percutaneous irradiation with cyclophosphamide medication in the intervening periods. According to the results, a plasma ribonuclease determination to check the result of therapy should only be performed at an interval of 2 weeks after each therapy step.