Development of Methodology for the Measurement of Prostacyclin and Thromboxane Production: Possible Relevance of Prostacyclin/Thromboxane Balance in Clinical Conditions

This thesis describes the historical development of our knowledge of prostaglandins and thromboxane and the synthesis, metabolism and actions of prostacyclin and thromboxane. Chapter 3 then presents work on the development and validation of a radioimmunoassay to measure plasma prostacyclin metabolite levels. Comparisons are made of results using a tritiated and an iodinated radioactive label and also of results obtained using different antibodies. Results are also presented of an assay to measure prostacyclin stimulating factor in normal plasma and serum. A method developed to measure endothelial cell prostacyclin production using a human umbilical artery perfusion model is described. Chapter 4 describes the various methods which may be used to measure production of thromboxane A2. Firstly a radioimmunoassay is described which measures thromboxane B2 the stable metabolite of thromboxane A2 and results using this assay for both plasma and serum samples are produced. Methods for measuring thromboxane generation by platelets in response to aggregation with 4 ug/ml of collagen and also serum thromboxane B2 levels in bleeding time blood are described. The second part of the thesis is concerned with an attempt to validate the relevance of the prostacyclin/thromboxane balance in clinical situations. Possible ways of altering the thromboxane/prostacyclin balance which may have clinical implications were explored. Plasma levels of prostacyclin metabolites and thromboxane before and after ingestion of drugs known to alter arachidonic acid metabolism are shown. Studies on the effect of dietary fat intake and smoking on the prostacyclin/thromboxane balance are presented. Chapters 6 and 7 examine the thromboxane/prostacyclin balance in a range of vascular diseases and in bleeding disorders respectively. A Chapter is then devoted to the possible relevance of the thromboxane/prostacyclin balance in pregnancy and associated disorders of pregnancy. Chapter 9 summarises the results of this work and also discusses the implications for future research