Age-related changes of serum apoprotein SASSAM, apoprotein A-I and low-density lipoprotein levels in senescence accelerated mouse (SAM).

Age-related changes of serum concentration of apo SASSAM, an apoprotein of high density lipoprotein (HDL) which cross-reacts with antiserum against murine senile amyloid fibril protein (ASSAM) were estimated in senescence accelerated mouse (SAM-P) and in senescence resistant series (SAM-R), as a control, using a single radial immunodiffusion technique. Serum concentrations of apo A-I, a major apoprotein of HDL, and low density lipoprotein (LDL) were also measured. In SAM-P (SAM-P/1 and SAM-P/2) with a high incidence of senile systemic amyloidosis, we observed age-associated decreases in serum apo SASSAM levels. The concentrations of apo SASSAM at 16 months of age were below 40% of the concentration at 2 months of age, regardless of the sex. In contrast with SAM-P, we observed no age-associated decrease of serum apo SASSAM levels in SAM-R (SAM-R/1 and SAM-R/2) with a low incidence of amyloidosis. Serum apo SASSAM concentration was higher in SAM-R/1 than in any other strain of mice observed. Serum apo A-I concentration was highly and significantly correlated with the serum concentration of apo SASSAM and decreased with advancing age in SAM-P but not in SAM-R. Age-related changes of LDL were not observed in any strain, but the concentration was lower in the females. In old SAM-P (16 months' old), the concentration of apo SASSAM decreased to one-third of that in the young SAM-P (4 months' old) and the serum concentrations of albumin and total protein did not decrease, compared with those in the young mice. All these findings taken together suggest that abnormality of metabolism in apo SASSAM, putative precursor of ASSAM, might occur in SAM-P.