Serum amyloid P component regulation by sex steroids in rats

Serum amyloid P component (SAP) has been designated as a female protein in hamsters. To investigate the effects of sex steroids on SAP concentration in rats, SAP was purified from Wistar rats by affinity chromatography. Anti-SAP was raised. Sample sera were obtained from 150 young and old rats, after which, they were injected with either estradiol (E2), testosterone (T), or dehydroepiandrosterone (DHA). Sera were serially obtained from the tail vessels until the 8th day after injection. Serum levels of SAP were measured by micro single radial immuno-diffusion with a standard pooled serum as 100%. As the rats aged, the SAP levels in untreated female rats increase with age from 93% at 11 weeks to 346% at 58 weeks. In 28-week-old rats, the SAP levels in females (135 +/- 40%) were significantly (p less than 0.01) higher than those in males (80 +/- 32%). When old female rats (56 wk) were injected with DHA (3.5 mg), the SAP decreased significantly (p less than 0.01) to 70.8% of the preinjection level on the 8th day after injection. When young male rats (11 wk) were jnjected with E2 (0.5 mg), the SAP levels increased rapidly to 188% of the prelevel on the 5th day. Serum E2 levels reached a peak on the 2nd day. After the injection of T, the SAP levels did not change.