Background: The quail and chicken major histocompatibility complex (Mhc) genomic regions have a similar overall organization but differ markedly in that the quail has an expanded number of duplicated class I, class IIB, natural killer (NK)-receptor-like, lectin-like and BG genes. Therefore, the elucidation of genetic factors that contribute to the greater Mhc diversity in the quail would help to establish it as a model experimental animal in the investigation of avian Mhc associated diseases.

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We have identified three members of the heat shock protein (HSP) 70 family from the Japanese quail, Coturnix japonica. The coding regions of the genes, CjHSPA2, CjHSPA5 and CjHSPA8, exhibit more than 96% similarity to related genes in the chicken, GgHSP70, GgHSPA5 and GgHSC70. The putative proteins encoded by the quail genes contain motifs considered essential for HSP70 family members. In addition, the predicted proteins are more similar to HSPA2, HSPA5, and HSPA8 proteins from vertebrates than they are to other members of the HSP70 family. As is true for orthologs from chicken and mammals, the quail genomic loci consist of a single exon (CjHSPA2) or eight exons (CjHSPA5 and CjHSPA8). The promoter regions of the genes also contain conserved motifs and are similar in structure to promoter regions of related genes in other species. Furthermore, gene order in the regions surrounding the quail HSP70 has been preserved, providing evidence that the genomic regions are orthologous to HSP70-containing regions in the chicken genome. One of the quail HSP70-related genes, CjHSPA2, exhibited a robust response to heat shock treatment and transcription of CjHSPA8 mRNA was weakly induced by heat treatment. Taken together, the data suggest that CjHSPA2, CjHSPA5 and CjHSPA8 encode orthologs of HSPA2, HSPA5 and HSPA8 with the notable difference that CjHSPA2 and CjHSPA8 are heat shock-inducible genes, whereas HSPA2 and HSPA8 are constitutively expressed in a heat shock-independent manner.

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In splenectomized Thoroughbred horses (Group S), the plasma haptoglobin (Hp) concentration was increased by the operation but thereafter significantly decreased to a lower level than before the surgery. The red cell haemolysis rate in a hypotonic salt solution and haemoglobin (Hb) binding Hp after exercise in Group S were significantly lower than in control horses (Group C). These results suggest that: 1) the spleen accelerates the fragility of the red cell membrane; 2) osmotic sensitive red cells are easy to haemolyze during exercise; and 3) the haemolysis during exercise increases the Hb-binding Hp level in plasma and then accelerates the synthesis of Hp in liver. Therefore, plasma Hp is a clinical indicator of red cell membrane fragility and haemolysis in a blood vessel during exercise.