cyclic-gmp and Intestinal-Neoplasms

The cGMP signaling axis has been implicated in the suppression of intestinal cancers, but the inhibitory mechanism and the extent to which this pathway can be targeted remains poorly understood. This study has tested the effect of cGMP-elevating agents on tumorigenesis in the

Topics: Adenomatous Polyposis Coli; Animals; Apoptosis; Cell Proliferation; Cell Transformation, Neoplastic; Cyclic GMP; Female; Guanylyl Cyclase C Agonists; Intestinal Neoplasms; Male; Mice; Mice, Inbred C57BL; Peptides; Precancerous Conditions; Sildenafil Citrate

The adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) levels were determined in the small and large intestinal tissue of rats that had been exposed to single and chronic administration of the colon carcinogen 1,2-dimethylhydrazine (DMH). A single subcutaneous injection of DMH resulted in a decrease in the intracellular concentration of cAMP and increase in cGMP beyond the levels which had been measured in the unexposed intestinal tissue and DMH induced intestinal adenocarcinomas. Recovery to normal concentrations of the cyclic nucleotides occurred within 30 days. Multiple exposures resulted in maintaining reduced levels of cAMP while cGMP was also found to be lowered upon the chronic administration. A possible explanation for these observations is the expansion of the crypt cell population consisting of replicating intestinal cells that occurs upon exposure to the carcinogen. These findings suggest that cyclic nucleotide alterations may represent a characteristic of the precancerous state of intestinal tissue and indicates further studies are warranted to determine whether these changes may serve as a useful marker in a screening program for colon cancer.

Topics: Adenocarcinoma; Animals; Colonic Neoplasms; Cyclic AMP; Cyclic GMP; Dimethylhydrazines; Injections, Subcutaneous; Intestinal Neoplasms; Kinetics; Male; Precancerous Conditions; Rats

Sperm positive 12-14-day pregnant Holtzman rats were exposed to a single subcutaneous injection (20 mg/kg body wt) of 1,2-dimethylhydrazine (DMH). Two days post-exposure, the fetal intestinal tissues were examined for their content and metabolic activities for cyclic 3',5'-adenosine monophosphate (cAMP) and cyclic 3',5'-guanosine monophosphate (cGMP). The in utero exposure to the carcinogen resulted in lowering the intracellular content of cAMP and increasing cGMP. The decreased levels of cAMP may be accounted for the finding of a corresponding increase in its breakdown by its phosphodiesterases; however, associated with the increase in cGMP was correspondingly an increase in its phosphodiesterases, suggesting the activities for synthesis of this cyclic nucleotide may be the major factor for its elevated concentration. These observations indicate that DMH may cross the placental barrier and can effect the intracellular cyclic nucleotide concentrations in the fetal tissues as well as acting as a colorectal carcinogen in the adult rat. The changes in the cyclic nucleotide levels were toward the direction expected for an increased cell proliferation; consequently, further investigations are suggested to determine whether a hyperproliferative state is induced by the DMH in the already rapidly dividing fetal intestinal tissue.

Topics: Animals; Cyclic AMP; Cyclic GMP; Dimethylhydrazines; Female; Fetus; Intestinal Neoplasms; Intestines; Methylhydrazines; Neoplasms, Experimental; Pregnancy; Rats

The intracellular concentrations of adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) were determined in adult male Holtzman rat small intestinal tumors induced by subcutaneous administration of 1,2-dimethylhydrazine (DMH) or X-irradiation of only the hypoxic ileum and jejunum. The levels of cAMP and cGMP in the cancer cells from DMH-treated animals were 50% and 200%, respectively, of the values measured for intestinal tissue. The amounts of cGMP in the lesion of the X-irradiation induced rat small bowel adenocarcinoma determined in the present investigation and of cAMP measured previously were observed to be only 50% of the value for unirradiated intestine. It has thus been shown that in the DMH-induced colon and small intestinal tumors, the X-irradiation induced rat small bowel adenocarcinoma and the human colon adenocarcinoma, the cAMP concentrations are consistently about 50% of the levels measured in comparable normal tissues. These findings of diminished intracellular cAMP concentrations imply a serious cellular defect mechanism occurring in intestinal cancer. However, there appears to be no similar pattern of change for the intracellular concentrations of cGMP, which suggests that different biochemical pathways exist in these malignancies.

Topics: Adenocarcinoma; Animals; Cyclic AMP; Cyclic GMP; Dimethylhydrazines; Intestinal Neoplasms; Intestine, Small; Male; Neoplasms, Experimental; Neoplasms, Radiation-Induced; Rats