Vascular endothelial growth factor is increased following coronary artery occlusion in the dog heart

Vascular endothelial growth factor (VEGF) is a hypoxia-inducible factor expressed into several molecular forms in mammalian tissues of which VEGF 120, VEGF 164, and VEGF 188 are the major isoforms. While VEGF 164 is the predominant isoform in most tissues, VEGF 188 has been reported to be dominant in cardiac tissues such as that in guinea pig, rat, and mouse. In the dog heart, an important model for studies of myocardial ischemia and angiogenesis, the expression of VEGF remains to be established. We investigated the expression of the various isoforms of VEGF in normal and ischemic dog heart tissues using Reverse transcription-Polymerase chain reaction, Ribonuclease Protection Assay and Western blotting. The nucleotide sequences of the major isoforms of VEGF were also determined using homology cloning techniques. Our study showed that the nucleotide sequences of dog VEGF were highly homologous to human VEGF especially in the c-terminal region spanning exons 58. A single amino acid-deletion (Glu5 in human VEGF), similar to that reported in other animal species, was observed in the major isoforms resulting in monomers of 120, 164, and 188 amino acids. A novel splice site similar to that in human VEGF183 was also identified in the dog heart, resulting in the 182 amino acid-containing isoform (VEGF 182). Moreover, VEGF 164 was expressed at a higher level as compared with VEGF 182 or VEGF 188 in both normal and ischemic tissues. The identification of the nucleotide sequences of VEGF isoforms in the dog heart should prove useful in investigating the molecular expression of VEGF in canine tissues.