SERUM AMYLOID-A GENE-EXPRESSION IN RABBIT, MINK AND MOUSE

The expression of serum amyloid A (SAA) protein, a major acute-phase r eactant in most species, was examined by in situ hybridization in mult iple organs of rabbit, mink and mouse. In livers of unstimulated mice and rabbits a heterogeneous pattern of SAA expression in hepatocytes w as observed. In all three species, lipopolysaccharide (LPS) administra tion resulted in extensive uniform hybridization of SAA probes to hepa tocytes and in the rabbit SAA transcripts were detected in cells in th e white pulp of the spleen, the adrenal cortex and ovary as well as in the mucosa and lymphatic vessels of the small intestine. Examination of hybridizing SAA signals in the rabbit myocardium showed a speckled distribution in myocytes. The rabbit endocardium was strongly positive , and in the kidney rabbit SAA mRNA was mainly confined to epithelial cells of the proximal and distal convoluted tubules. In the unstimulat ed mouse, SAA mRNA was detected in the liver and epithelial cells of t he small and large intestine. After stimulation of an acute-phase resp onse with LPS a strong response was seen in these organs as well as in the convoluted tubules of the kidney. In extrahepatic organs of the m ink, no SAA mRNA was detectable in unstimulated animals, while the con voluted tubules of the kidney and uterine endometrium were strongly po sitive after systemic LPS injection.