Growth, differentiation and the beta-adrenergic signal system of HL-60 cells. Characterization in a medium with insulin as the only added protein

Epinephrine induces beta-adrenergic desensitization and differentiation of HL-60 cells

The HL-60 cell line was cultured in a serum-free medium and exposed to various concentrations of EPI. The effects on cell growth, differentiation and beta-adrenergic response were followed during the culture period of 72 h. Short-term exposure (3 min) to EPI (1 nM-1 mM) in the presence of theophylline (4 mM) caused a dose-dependent increase of cAMP levels with a maximum of 1500% above basal levels. When the cells were exposed to EPI (1 nM-10 microM) for 72 h, a dose-dependent increase of cAMP levels with a maximum of 60% above basal levels. Sustained exposure to EPI generated a dose-dependent desensitization of the beta-adrenergic signal system. After EPI treatment for 72 h, IPR (10 microM for 3 min) in the presence of theophylline (4 mM) increased cAMP-levels by only 80% above baseline level (cAMP levels after maintained exposure to EPI), compared to 1080% above unstimulated level in control cells. The alpha-adrenergic receptor blocker PHENT (10 microM) did not affect baseline cAMP level or IPR-dependent cAMP response, but a mixture of EPI and PHENT increased the response to IPR. The HL-60 cell growth was not influenced by EPI. However, after repeated exposure to EPI for 72 h a concentration-dependent increase of HL-60 differentiation was demonstrated. Differentiation was not influenced by PHENT. These results suggest a differentiation induction due to a beta-adrenergic-induced cAMP elevation.

Growth of cells in a new defined protein-free medium

The development of a new stable synthetic serum replacement (SSR) is described, which allows the cultivation of mammalian cells in a defined, protein-free medium containing only dialyzable components. With a low concentration of insulin (RPMI-SR2 medium), growth rates of the transformed cell lines L929, HELA S3, and the hybridoma 1E6 were comparable to growth rates obtained with a serum-containing medium. The same medium also supported long-term cultivation of non-dividing mouse macrophages. The main principle of SSR is a metal ion buffer containing a balanced mixture of iron and trace metals. Stability against precipitation of important metals is achieved by the combined use of EDTA and citric acid as chelating agents. Efficient iron supply is mediated through the inclusion of the compound Aurintricarboxylic acid as a synthetic replacement for transferrin. SSR also contains a growth-promoting surfactant, Pluronic F68. Thus SSR provides a general foundation for growth and differentiation normally provided by serum. Limitations of other serum-free medium designs are discussed here: 1) the inability of transferrin to chelate all metals in the medium; and 2) the use of inorganic iron salts or iron citrate as an iron supplement leads to rapid precipitation of iron hydroxide in the medium. Both these problems are solved in the design of SSR.

Expression and function of beta-adrenergic receptors in human hematopoietic cell lines

We investigated the expression and functional characteristics of beta-adrenoceptors in a panel of 10 phenotypically different human hematopoietic cell lines. A binding assay with [125I]iodocyanopindolol as the ligand revealed that cell lines of myelomonocytic or histiocytic derivation (HL-60, ML-2, RC-2A, U-937) expressed high numbers of beta-adrenoceptors. An intermediate density of receptors was found in a non-T, non-B cell leukemia line (Nall-1), whereas T-cell (JM, CCRF-CEM), B-cell (Raji) or erythroleukemic cell lines (K-562, HEL) displayed minimal or undetectable binding of the radioligand. Isoprenaline-stimulated cAMP production by the cells correlated to their extent of beta-adrenoceptor expression. Southern blot hybridization analysis of genomic DNA from the cell lines with a 32P-labelled beta 2-adrenoceptor cDNA probe revealed no evidence for major rearrangement or amplification of the receptor gene. Incubation with isoprenaline in vitro suppressed the proliferation of the receptor-rich RC-2A cells but did not affect the growth rate of the receptor-deficient K-562 cells. Treatment with propranolol slightly enhanced the proliferation of the RC-2A cells but did not markedly alter the growth rate of two other cell lines, regardless of their beta-adrenoceptor status. These findings indicate a regulatory influence by the sympathoadrenergic system on selected cells of the myelomonocytic lineage.