Increased fluidity of serum lipids and development of spontaneous mammary tumors in C3H mice

Abstract

The degree of lipid fluidity (LFU) was quantitatively monitored by fluorescence polarization analysis of the hydrocarbon fluorescent probe diphenylhexatriene when embedded in artificial and biological lipid complexes. The results have shown a marked increase in LFU in serum lipids associated with the development of spontaneous mammary tumors in C3H mice. An increase in serum LFU was observed during the initiation of primary tumors. The serum LFU further increases as a function of increase in the tumor volume. This increase was not observed when animals were given transplants of syngeneic, spontaneously arising mammary tumors or following implants of antigenically inert glass beads. Since the serum LFU in C57BL/6, NZB and A/JAX non-tumor-bearing mice was found to be significantly lower than in C3H non-tumor-bearing mice, it is suggested that alterations in the dynamics of serum lipids in the C3H system may have a direct relation to the induction and/or growth of spontaneous tumors in these mice. Moreover, experiments carried out with an artificial membrane model system have shown that the dynamics of a lipid complex are directly determined by its lipid composition. The three major parameters that determine the LFU of a lipid domain are: (a) the relative amounts of different phospholipids; (b) the molar ratio of cholesterol to phospholipids; and (c) the degree of saturation of the fatty acids. It is therefore suggested that alterations of this kind may occur in serum lipids during spontaneous mammary tumor development in C3H mice.