Glass, Rainer; (2001) Purinergic signalling in endocrine organs: Testis, thyroid, thymus. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The expression of receptors for extracellular purines and pyrimidines was investigated by immunohistochemistry, in situ hybridisation and western blotting in endocrine organs of male, adult rats. All seven subtypes of ATP gated cation channels (P2X receptors) were investigated in two 'classical' endocrine organs, the testis and the thyroid; P2X receptors and two subtypes of the G-protein coupled receptors for purines and pyrimidines (P2Y₁ and P2Y₂ receptors) were studied in a 'non-classical' endocrine organ, the thymus. Functional studies on the role of P2X receptors on cultured vascular endothelial cells were performed. Immunohistochemical investigation of the testis showed that P2X₂, P2X₃, P2X₅ and P2X₇ are expressed differentially in germ cells throughout the cycle of the seminiferous epithelium. P2X receptors were detected in vascular smooth muscle and were found in Sertoli cells throughout all stages of gametogenesis. Immunohistochemical, immunofluorescence and immunoblotting studies of the thyroid were carried out using two different sets of antibodies for P2X receptors. Thyroid follicular epithelial cells, vascular smooth muscle and endothelial cells all stained for different combinations of P2X receptor subtypes. Studies on the thymus revealed that P2X and P2Y receptors are differentially expressed in the thymus. P2X receptors were most abundant and P2Y₂ receptor were exclusively expressed in T-cells of the thymic cortex, where T-cell proliferation and apoptosis take place. P2X receptors were also detected in thymic epithelial cells and the vasculature (smooth muscle cells and endothelial cells). Endothelial cells were cultured and the expression of P2X receptors was monitored by immunofluorescence. The P2X₄ and P2X₆ receptor subtypes were found to be expressed on the cell membrane. P2X₆ receptors were shown to be associated with the cell-adhesion molecule VE-cadherin. The roles of P2X and P2Y receptors in the mediation of cellular differentiation, proliferation, apoptosis and cell-adhesion are discussed.

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