Developmental regulation of expression of rabbit C-reactive protein and serum amyloid A genes.

Serum amyloid A (SAA) and C-reactive protein (CRP) are acute phase plasma proteins which increases 100- to 1000-fold after inflammatory stimuli. In this study pregnant rabbits were given lipopolysaccharide (LPS) or subjected to laparotomy with fetal injections of LPS at different stages of gestation. Newborn rabbits were given LPS or saline. SAA and CRP mRNA were studied using Northern blot analyses and scanning densitometry. In vitro transcribed RNAs were used as standards for quantitative mRNA analyses. A gradual increase in LPS-induced SAA and CRP mRNA levels was observed during development, but only SAA mRNA induction was seen at gestational day 19. Fetal SAA and CRP mRNA induction was not seen after maternal LPS stimulation. The constitutive level of SAA and CRP mRNA was significantly lower in fetal rabbits than in adults. The control level of SAA mRNA in one-day-old rabbits was higher than the normal adult level, while the neonatal CRP mRNA level was lower. SAA2 seemed to be the major acute phase reactant in both fetal, neonatal and adult rabbits, while relatively more SAA3 was found during early developmental stages. The study demonstrated that CRP and three SAA genes are differentially regulated during development.