Hamster female protein, a sex-limited pentraxin, is a constituent of Syrian hamster amyloid.

Female protein (FP) is a pentraxin of Syrian hamster which is a homologue of two human pentraxins, C-reaction protein (CRP) and amyloid P component (AP). Functionally, FP has been shown to be similar to CRP, although FP has more homology at the amino terminus with AP. The present work investigated amyloid in the Syrian hamster to determine whether FP was involved in a manner analogous to AP. FP was found to be a constituent of Syrian hamster amyloid. This conclusion was based on the following results: (a) FP was consistently detected in amyloid deposits by fluorescent microscopy with specific antisera; (b) The amount of FP extractable from hamster livers directly correlated with the presence of amyloid; and (c) 125I-FP injected intravenously into amyloidotic hamsters rapidly left the intravascular compartment and was found subsequently in amyloid deposits. This unusual alteration of plasma metabolism and amyloid localization of 125I-FP was a characteristic finding in amyloidotic hamsters and was specific for 125I-FP. Therefore, as an amyloid component, FP appears to be functionally similar to human AP. However, FP synthesis is under sex steroid control and the unique sex-limited expression of this pentraxin was associated with an equally novel propensity for deposition of amyloid in female hamsters under normal or experimental conditions. Thus, a high serum level of FP, as found in normal females or diethylstilbestrol-treated males, was associated with enhanced amyloidosis. Although speculative at present, a primary role for serum FP in hamster amyloid deposition may be experimentally approachable by hormonal manipulation of FP synthesis.