DECREASED CYCLIC INOSITOL PHOSPHOHYDROLASE ACTIVITY IN HAMSTER RENAL TUMORS AND HUMAN RENAL-CELL CARCINOMAS

Cyclic inositol phosphohydrolase (cIPH) (EC 3.1.4.36) hydrolyzes the c yclic phosphodiester bond of cyclic inositol monophosphate to yield in ositol l-phosphate. Renal tissue in various species has been shown to contain the highest activity of this enzyme. Cyclic inositol monophosp hate, the substrate for this enzyme, has been implicated in the regula tion of cell density. Thus, we determined whether activity of this enz yme is modulated in renal tumor. Samples of hamster renal tumors induc ed by diethylstilbestrol (DES) demonstrated 87% less cIPH activity tha n control hamster kidney. After 8 days of DES treatment of hamsters, a 28% decrease in the cIPH activity in kidney was observed. Interesting ly, comparison of the cIPH activity in normal human kidney cortex, med ulla, and renal cell carcinoma gave the following values (mean +/- SD) , 10.6 +/- 4.6 (9), 6.7 +/- 4.6 (5), and 1.9 +/- 2.3 (8), respectively . Our study demonstrates that cIPH activity is reduced in hamster and human renal tumors. (C) 1995 Academic Press, Inc.