Calcitonin stimulates growth of human prostate cancer cells through receptor-mediated increase in cyclic adenosine 3',5'-monophosphates and cytoplasmic Ca2+ transients

Our recent study has shown that a calcitonin (CT)-like immunoreactive substance(s) is secreted by cultured prostate cells, and secretion of this material is significantly higher in malignant than in benign prostate cells. To test the hypothesis that prostatic CT may serve as a paracrine/neuroendocrine factor, the present study investigated for the presence of CT receptors in the prostate gland. Signal transduction mechanisms activated by CT were examined, and the study also tested its effects on prostate cell proliferation, as assessed by [3H]thymidine incorporation. The results show that high affinity binding sites for [125I]salmon CT were present in plasma membrane fractions of human prostate tissue specimens and the prostate cancer LnCaP cell line. The maximal binding for CT receptors was 564 +/- 163 fmol/mg protein, and the apparent dissociation constant (Kd) was 2.89 +/- 0.58 nM. CT induced a dose-dependent increase in cAMP generation in LnCaP cells. The effect of CT on cytoplasmic Ca2+ transients of LnCaP cells was examined by videofluoromicroscopy. CT (100 nM) induced a rapid and sharp increase in cytoplasmic Ca2+ concentrations in LnCaP cells. The CT-induced increase in cytoplasmic Ca2+ transients appeared to be biphasic (spike and plateau), and this increase was 4- to 10-fold during the initial phase. The profile of this response is characteristic of the activated Ca2+/phospholipid second messenger system. CT also caused a dose-dependent increase in [3H]thymidine incorporation by LnCaP cells. These results suggest that a locally secreted CT-like peptide(s) induces mitogenic responses in prostate cancer cells. This action seems to be mediated through activation of signaling mechanisms, leading to the accumulation of two different second messengers, cAMP and calcium. Activation of dual second messenger systems by CT receptors suggests that the peptide hormone may play an important role in rapidly growing cell populations during the process of tumor formation.     

Characteristics of microwave and thermal heating of samples of cell suspensions and solutions of several compounds

The influence of microwaves and heat on dynamics of heating of samples of intact and inactivated bacteria Escherichia coli and solutions of some basic molecular components of cell was investigated. It was shown that microwaves induce different dynamics of heating of all samples. On the contrary, thermal action induces identical dynamics of heating of all this samples except vegetable oil which was heated more intensively.