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Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide with widespread occurrence in the nervous system and peripheral organs, including the mammary gland. Previously, we have shown that PACAP38 is present in the human milk at higher levels than in respective blood samples. However, it is not known how PACAP levels and the expression of PAC1 receptor change during lactation. Therefore, the aim of our study was to investigate PACAP38-like immunoreactivity (PACAP38-LI) in human colostrums and transitional and mature milk during lactation and to compare the expression of PAC1 receptors in lactating and non-lactating mammary glands. We found that PACAP38-LI was significantly higher in human colostrum samples than in the transitional and mature milk. PACAP38-LI did not show any significant changes within the first 10-month period of lactation, but a significant increase was observed thereafter, up to the examined 17th month. Weak expression of PAC1 receptors was detected in non-lactating sheep and human mammary glands, but a significant increase was observed in the lactating sheep samples. In summary, the present study is the first to show changes of PACAP levels in human milk during lactation. The presence of PACAP in the milk suggests a potential role in the development of newborn, while the increased expressions of PAC1 receptors on lactating breast may indicate a PACAP38/PAC1 interaction in the mammary gland during lactation.

Damage caused by oxidative stress is involved in many types of diseases, including breast cancer. Our aim was to detect the oxidative stress parameters and blood plasma changes with differential scanning calorimetry (DSC) in breast cancer patients. The study included 40 adult breast cancer women who were grouped according to tumor diameter, regional lymph node metastases, proliferative activity, receptor status and postoperative chemotherapy. To monitor oxidative stress, malondialdehyde, oxygen free radicals (OFRs), activity of myeloperoxidase (MPO), superoxide dismutase (SOD) and catalase (CAT) were measured. Denaturation of plasma components was detected in Setaram Micro DSC-II calorimeter. The total production of OFRs, the MPO activity and lipidperoxidation were significantly increased in each breast cancer patients considering the tumor size, the metastatic lymph nodes, the proliferation activity and receptor status compared with healthy controls (p \ 0.05). These pro-oxidants were slightly elevated without chemotherapy, but their values were increased significantly in chemotherapy-receiving group. The activity of SOD and CAT was significantly decreased in all groups, and in regard to the chemotherapy, they were changed significantly parallel to the severity of disease. Regarding to both the increased tumor diameter and the increased number of affected lymph nodes, DSC measurements showed a strong relationship between the maximum excess heat capacity (C pmax ) of the blood plasma and the severity of disease. The study demonstrated that oxidative stress is implicated in breast carcinoma and chemotherapy aggravates these changes which confirmed the plasma DSC measurements also.

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