Amyloid and Female Protein: Sex-Related Occurrence in the Syrian Hamster

Abstract

The prevalence of amyloidosis in Syrian hamsters has been reported in a variety of reports (1–3). Our interest in hamster amyloid was related to previous studies on an unusual protein, female protein (FP), found in the serum of these animals (4). Female protein was shown to be a homologue of serum amyloid P component (SAP) and C-reactive protein (CRP) (5). However, FP synthesis was regulated by sex steroids so that normal males had serum levels about 100- to 200-fold less than females. Actually, FP was present at extraordinarily high levels in female hamster serum (1–3 mg/ml) when compared to the usual CRP-SAP homologues in other mammals. Functionally, FP shared a very characteristic function with CRP, i.e., a Ca⁺⁺ dependent phosphorylcholine (PC) binding capacity (5) with attendant complement activation (6). However, at the amino terminus, FP was structurally more similar to SAP (5). The question arose whether FP also could have a “SAP-like” role as an amyloid constituent. The results of this study indicated that FP was indeed an amyloid constituent. Furthermore, amyloid deposition was correlated directly with serum FP levels, suggesting more than a passive role of FP in pathogenesis of this disease. In addition, the metabolism of injected ¹²⁵I-FP was found to be characteristically altered in presence of amyloid (7).