Análise de elementos traço presentes em tecidos mamários canino através da técnica de fluorescência de raios X

Abstract

Studies with dogs show that the breast cancer represent about 25% to 50% of tumor types. Of this total, half is considered malignant. Despite representing a considerable amount of malignancy, studies in this area are few representative and scarce in the literature. It is known that tumors are caused by chemical and biochemical changes that occur in the cell. Currently, surveys are conducted to understand the behavior of these changes and for this reason, it is of great value to know the trace elements present in these tissues. For this purpose, the most common technique is to ED-XRF (X-Ray Fluorescence Energy Dispersion) since it is a non-destructive analytical technique to determine and quantify the elemental composition of the samples, although it doesn’t identify elements with low atomic numbers (less than Z= 10). Were analyzed 56 samples of canine breast tissue benign and malignant, fixed in 10% buffered formalin and kept at ambient temperature. First, for the measurement of trace elements Ca, Fe, Cu and Zn were determined standards for calibration curves diluted in water to concentrations of Ca, Fe, Cu and Zn, ranging from 400 mg/kg to 35 mg/kg, from 20 mg/kg to 2 mg/kg, from 10 mg/kg to 1 mg/kg and from 100 mg/kg to 9 mg/kg, respectively. Measurements were subjected to ED-XRF technique using an X-ray tube with silver anode and exposure technique of 30 kV and 100 uA and exposure time of 1000 seconds (uncertainty ≤ 3%). The XRMC code (X-Ray Monte Carlo) was used for validation of experimental method, which is intended to simulate by computer the expected responses for experimental tests, therefore validating the methodology efficiency. The concentrations of trace elements obtained were analyzed statistically where there was a significant variation of Zn element, the latter being present in higher concentration in malignant breast tissue than benign. This result may be related to the presence of this element in the matrix metalloproteinases, and malignant neoplasms are more concentrated because there are characteristic of tumor invasion in this type of neoplasm. In another statistical comparison it can be seen that the trace elements Fe, Cu and Zn is equivalent concentration both in the central region of the tumor as well as in the periphery, with the exception of Ca, this focusing more on the tumor region may be due to calcifications. Studies in this area are of great potential for allowing a better understanding of the disease process in canine mammary tumors.