Neokyotorphin and neokyotorphin (1-4): secretion by erythrocytes and regulation of tumor cell growth.

Human erythrocytes release neokyotorphin, the 137-141 fragment of hemoglobin alpha-chain into the supernatant of red blood cells primary culture. However, the neokyotorphin fragment 1-4 that is formed together with neokyotorphin inside the red blood cells and in various tissues is not found in the supernatant. Both neokyotorphin and its 1-4 fragment were shown to stimulate proliferation of L929 tumor cells.

Cytotoxic activity of acetylcholine receptor ligands.

Acetylcholine receptor ligands were studied for cytotoxicity in K562 human erythroid leukemia tumor cells. Cytotoxicity of carbachol, an agonist of acetylcholine receptors, atropine, an antagonist of muscarinic acetylcholine receptor, neurotoxin 11 (NT II) from Naja naja oxiana cobra venom and tubocurarine, antagonists of acetylcholine receptor of nicotinic type was exhibited in the 10-7-10-5 M concentration range. Several cytolytic processes, two for carbachol and three for other ligands, corresponding to different concentrations of each ligand were detected.

Tumor cell cytolysis mediated by valorphin, an opioid-like fragment of hemoglobin beta-chain.

Valorphin, an endogenous opioid-like hemoglobin fragment, is cytotoxic for L929 and K562 tumor cells in 10(-7)-10(-13) M concentration range. Because cytolytic effects induced by valorphin in K562 cells are inhibited by naloxone, opioid receptors should be involved in induction of valorphin-mediated tumor cell death. Three distinct cytolytic processes, differing in the onset time and the development time, take place with K562 cells within 10-18 h of incubation with valorphin.

Cytolytic processes induced by TNF in L929 and K562 differ in DNA fragmentation mechanisms.

Objective: Cytolytic activity of TNF was analysed at L929 and K562 tumor cell lines.

Methods: TNF-mediated cytotoxicity was studied within 10(-6)-10(-17) M concentration range after 18 h of incubation with target cells.

Results: TNF caused reliable cytotoxicity values in both cell lines, while L929 cells were more sensitive to cytolytic action of the protein than K562 cells.

Neokyotorphin and neokyotorphin (1-4): cytolytic activity and comparative levels in rat tissues.

The content of biologically active hemoglobin fragment neokyotorphin (TSKYR) as well as that of neokyotorphin fragment (1-4) (TSKY) were determined in extracts of lung, heart, and brain tissue of rats. The content of both peptides as well as the neokyotorphin/neokyotorphin(1-4) ratio differed significantly from each other in these tissues. The respective parameters deviate considerably from those of erythocytes where these peptides are originally formed.