THE EFFECT OF NEUROPEPTIDES KYOTORPHIN AND NEOKYOTORPHIN ON PROLIFERATION OF CULTURED BROWN PREADIPOCYTES

Stimulation of DNA and protein synthesis in brown preadipocytes by 1 m u M neokyotorphin in serum-containing media was comparable with the ef fect of 1 mu M norepinephrine. In serum-free medium a decrease and a s hift of the maximal effect to lower concentration of neokyotorphin wer e observed, Kyotorphin had no effect on cell proliferation in either m edium; however, 0.01-1 mu M kyotorphin inhibited the cell proliferatio n stimulated by 1 mu M norepinephrine. Norepinephrine and both peptide s stimulated comparable Ca2+ rise in freshly isolated brown preadipocy tes. The effects of neokyotorphin and norepinephrine were additive, wh ereas 0.03-0.3 mu M kyotorphin blocked the action of 3 mu M norepineph rine. The peptides did not affect the cAMP level in non-stimulated or norepinephrine-stimulated cultured cells, The effects of the peptides on the brown fat cell cultures indicate that peripheral tissue cells c ontain receptors for these neuropeptides. (C) 1997 Federation of Europ ean Biochemical Societies.