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Title: Type 1 angiotensin II receptors in bovine adrenocortical cells
Author: Dell, Ghislaine C.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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This thesis presents modifications to improve the established methods for the isolation and culture of zg cells, and characterises responses to steroidogenic agonists during short-term primary culture. The modified zg culture was used as a tool to pharmacologically characterise the type 1 AII receptor using Schild analysis in order to obtain pA2 values for a selective AT1 receptor antagonist, losartan (DuP753). The pA2 value is a measure of antagonist affinity which should be constant for the antagonist at a particular receptor subtype. The pA2 values obtained were compared to both pA2 values previously reported for boving zfr cell at AT1 receptors, and pA2 values calculated from cultured rat mesenteric artery smooth muscle cells. No significant difference was found in the pA2 values (zg : 7.02 +/- 0.20; vsmc : 7.45 +/- 0.31), indicating that pharmacologically the receptors are indistinguishable. The bovine AT1 receptor was then cloned, from bovine spleen, using the published bovine adrenal AT1 receptor sequence, by PCR. The resulting clones were sequenced and confirmed as AT1 receptors. The DNA was then used to probe for AT1 receptor mRNA expression in primary cultures of bovine zfr cells using Northern blot analysis. Specific agonists for the adrenal cortex, and second messenger analogues, were employed in these experiments. AII caused homologous downregulation (86%) of its receptor mRNA, an action found to be mimicked by stimulation of protein kinase C and calcium influx (91%). A cyclic AMP analogue (8-bromo cyclic AMP) also caused downregulation of AT1 receptor mRNA. In contrast, AT1 receptor mRNA was upregulated by incubation of the cells with insulin-like growth factor 1 (IGF-1) and potassium. Finally, the possibility that adrenal cortiscosteroids could exert a short-loop feedback effect on AT1 receptor mRNA was analysed. Cortisol, but no aldosterone, significantly downregulated (41%) the level of AT1 mRNA, which indicated a possible zone-specific effect on the regulation of AT1 receptors in the adrenal cortex. The results of these studies suggest that the physiological regulation of AII receptors within the adrenal cortex is more complex than has been previously considered.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available