Molan, Peter C.Elliott, Jennifer Lynn2026-08-202026-08-201994https://hdl.handle.net/10289/18557Bone growth in young mammals is a major determinant of eventual individual size, and ongoing bone metabolism is necessary to maintain a mineral balance for essential physiological processes. GH, IGF-I and IGF-II stimulate growth in many tissues and are implicated in cartilage and bone growth. Tissue sensitivity to a hormone may be gauged by receptor levels and the main objective of this thesis was to examine and characterise the receptors for GH and the IGFs in tissues of developing bone. Antler was used as a model for bone growth because it is similar in histochemistry to somatic long bones. It may be removed humanely, undergoes regeneration and grows rapidly, making it a useful tissue for research in growth. Receptor localization in tissues of the growing antler tip was determined using autoradiographical studies and the receptors were characterised using competitive binding assays and affinity cross-linking studies. Production of IGFBPs was assessed and analysed for interference of hormonal binding to receptors. Ontogeny of receptor distribution patterns over the antler growth phase was also studied to assess changes in localization, or implied function, occurring with tissue maturation. Administration of testosterone to deer bucks during the antler growth phase to induce precocious tissue maturation was used as a tool to assess the direct effects of circulating androgens on cartilage development, and changes to receptor localization relative to this treatment. No GH receptors were detected in antler tissues. IGF-I and IGF-II bound to receptors that had characteristics of type 1 and type 2 IGF receptors, respectively. Highest levels of IGF-I binding were in the maturation zone and IGF-II binding in the proliferative zone. IGFBPs were produced in higher levels in pre-cartilage than in cartilage tissues. Ontogenetic changes in IGF-I binding were observed by changes in distribution patterns at a late stage of antler growth. Distribution patterns of IGF-II binding did not change over the growth phase. Enhancement of antler mineralization and ossification was achieved to a limited degree by testosterone administration, suggesting that testosterone might not be as potent a stimulator of antler tissue maturation as its metabolites. In conclusion, antler growth is independent of direct stimulation by GH. IGF-I and IGF-II each preferentially bind to distinct receptor populations in antler tissues, with different tissue distribution, hormonal specificity and ontogeneticity. Localization of IGF receptors in antler tissues implied a role for IGF-I in matrixogenesis and a role for IGF-II in cell proliferation. IGFBPs were implicated in the regulation of IGF-II actions in vivo. This evidence suggests that antler tissue provides a unique opportunity to study the endocrine effects of IGFs on cartilage and bone.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.Thesis