Expression of integrin alphavbeta3 in pig, dog and cattle.

The alphavbeta3 integrin, also known as vitronectin receptor, is an adhesive glycoprotein that promotes angiogenesis in the embryo and tumors such as melanoma. Integrin alphavbeta3 is one of the receptors for adenovirus and hantavirus. There is little information on the constitutive expression of this integrin especially in animal species that are used for biomedical research. We used light and electron microscope immunocytochemistry and western blots to determine integrin alphavbeta3 expression in seven organs in the pig, dog and cattle. Immunohistology showed the integrin expression on the epithelium of small intestine, bile duct and renal proximal convoluted tubules in three species. The airway epithelium revealed a weak reaction for integrin alphavbeta3. Skin showed the integrin in occasional extravascular cells while skeletal muscles were negative. The integrin was expressed only in bronchial vasculature in the lung and occasional dermal microvessels. Many mononuclear cells in the lung and spleen stained for integrin alphavbeta3. Immunogold electron microscopy revealed the expression on the epithelium but not on the vasculature of the small intestine. Western blots detected integrin alphavbeta3 in small intestine and lung but not in skeletal muscles. We conclude the integrin is expressed on the epithelium but not in the vasculature. The expression differs strikingly among organs in the same species although the inter-species differences are minor. Restriction of the integrin to absorptive epithelia of small intestine and kidney may suggest its putative role in endocytosis. Because the integrin is a receptor for adenovirus, these data may be relevant to gene therapy studies.