The interaction of adriamycin with small unilamellar vesicle liposomes. A fluorescence study

Adriamycin inhibits PTH-mediated but not PGE2-mediated stimulation of cyclic AMP formation in isolated bone cells

We have examined the effect of adriamycin, an anthracycline antibiotic which modifies plasma membrane functions, on the cyclic AMP response to PTH and PGE2 in isolated osteoblastlike cells. Adriamycin blunted the increment in bone cell cyclic AMP caused by exposure to PTH. This effect appeared rapidly (within 3 min after bone cells were exposed to adriamycin) and disappeared soon after exposure of adriamycin-treated cells to adriamycin-free incubation medium. Inhibition was evident over the entire time course of PTH action, at low as well as high PTH concentrations, and was one-half maximal at 31 microM adriamycin. It could not be attributed to alterations in cyclic AMP exodus, degradation or interference with the cyclic AMP assay, nor to impaired cell viability. Adriamycin also reduced the stimulatory effect of PTH on adenylate cyclase activity in a crude plasma membrane preparation. By contrast, adriamycin failed to modify the effects of PGE2 on cyclic AMP generation in intact bone cells, and on adenylate cyclase activity in broken cells. Moreover, concentrations of adriamycin that blunted the effect of PTH on adenylate cyclase activity did not inhibit the stimulatory effects of sodium fluoride or of GppNHp. These results suggest that adriamycin selectively alters the interaction between PTH and its receptor or impairs the transmission of information from hormone-receptor complex to adenylate cyclase (or both), perhaps by binding to specific lipid domains in the plasma membrane. Structural analogues of adriamycin, which vary in their lipophilic properties, also varied in their capacity to perturb the cyclic AMP response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adriamycin causes up regulation of epidermal growth factor receptors in actively growing cells

We have demonstrated a drug-dependent increase in the capacity of HeLa and 3T3 cells, grown in the presence of lethal and sublethal concentrations of adriamycin, to bind epidermal growth factor (EGF). Scatchard analysis ascribes this effect to an increase in the number of binding sites, with little change in affinity. The time course of binding of 125I-EGF is unchanged by adriamycin treatment, in both 3T3 and HeLa cells, at both 0 and 37 degrees C. This increase appears gradually over 3 or 4 days' exposure to the drug and is reversible over a similar period. Although in HeLa cells the increase reaches a maximum of about 4-fold, regardless of cell density, the maximum observed in 3T3 cells, over 100-fold, is seen only at low cell densities. This could be related to the density-dependent growth regulation seen in 3T3 cells, but not in HeLa cells. We suggest that the ability of the anticancer agent adriamycin to alter the cellular response to a growth-regulatory substance may be related to the mechanism of its cytotoxic action.

Effects of adriamycin on heart and skeletal muscle chromatin

Interactions between adriamycin (ADM) and chromatin from heart and skeletal muscle from 15 day-old chicken embryos were investigated. Adriamycin interacts with the DNA of chromatin and this interaction is modified by the chromatin proteins. One of the effects of this interaction is an increase in the melting temperature (Tm) of the DNA, where adriamycin is observed to increase the Tm of heart chromatin to a greater extent than skeletal muscle chromatin. Adriamycin also inhibits in vitro DNA and RNA synthesis in isolated chromatin and nuclei. This inhibition is observed to be greater in heart muscle. Inhibition of transcription in the myocardium could be a major cause of adriamycin-induced cardiomyopathy.

Adriamycin-induced decrease of myocardial contraction reserve in rats treated with dobutamine

Muscle-mechanical and hemodynamic properties were measured in adriamycin-treated rats and in untreated controls. The respective parameters in both animal groups could not be distinguished at rest. Using a pharmacological stress test with dobutamine a differentiation of both groups was possible: the concentration-response curve of papillary muscles from ADM-rats was lower and shifted towards higher concentrations when compared with the respective curve of untreated animals. The maximum hemodynamic response following an i.v. bolus injection of dobutamine was considerably decreased in ADM-rats as compared to untreated rats. It is concluded that the estimation of impaired myocardial function due to adriamycin might be more accurate when the contraction reserve is evaluated.