Measurement of peripheral plasma corticosteroid concentrations by means of gas-liquid chromatography

Mason, Peter A (1976) Measurement of peripheral plasma corticosteroid concentrations by means of gas-liquid chromatography. PhD thesis, University of Glasgow.

Abstract

1. A method has been devised and evaluated for measuring the plasma concentrations of six major corticosteroids - aldosterone, 18-hydroxy-11-deoxycorticosterone (18 OH DOC), corticosterone, 11-deoxycorticosterone (DOC), cortisol and 11-deoxycortisol - using gas liquid chromatography (GLC) with electron capture detection. After extraction from plasma and both chromatographic and chemical purification, thermostable derivatives of the compounds were formed; beta-lactones of the 18-oxygenated steroids, aldosterone and 18 OH DOC; androstenes of the 17beta-hydroxylated steroids, cortisol and 11-deoxycortisol. Esterification of these derivatives with heptafluorobutyric anhydride (HFBA) formed enyl-heptafluorobutyrates which could be detected in quantities ranging from 0.3 pg for androstenetrione HFB to 2.3 pg for corticosterone 3, 21 bis HFB. 2. Accuracy, specificity, precision and convenience have also been assessed for each compound and discussed in relation to similar aspects of the performance of methods based on other techniques such as radioimmunoassay. Recovery of added steroid appeared to be quantitative in all cases and replicate variations of steroid values from a plasma pool were low in relation to the ranges of concentration experienced. Use of several GLC columns with differing separative properties indicated that discrete compounds were producing the chromatographic responses. The method has slightly lower capacity than the simplest steroid radioimmunoassay and a high degree of operator skill is needed to maintain efficient performance of the GLC. However, a physico-chemical method, such as GLC, for estimation of steroid levels has several distinct advantages over those based on saturation analysis. The principal one of these is the ease of setting up a method for a steroid which may be of only transient interest. In this case it would be a fairly simple matter to "add in" other steroids, such as 18-hydroxycorticosterone or cortisone, whereas with radioimmunoassay, considerable effort and expense would be required to produce the necessary antigens and antibodies. Investigation of the effects of some factors which influence adrenocortical secretion was undertaken. This allowed further evaluation of the method and also yielded new data. Levels of all steroids measured except aldosterone followed the diurnal rhythm of ACTH, although an effect on aldosterone may have been masked by changes in posture. Similarly, stimulation of endogenous ACTH by hypoglycaemia induced by insulin administration (insulin stress test) caused a rise in all steroid plasma levels. Infusion of exogenous ACTH uncovered a possible role of the hormone in electrolyte metabolism. Infusion rates designed to produce levels in the high physiological range caused very marked stimulation of DOC and corticosterone secretion - steroids with known mineralocorticoid properties. Angiotensin II, however, whether administered exogenously or raised by physiological manipulation caused stimulation of secretion of aldosterone only. Analyses were made in several pathological states; in 7 analyses of bilateral adrenal venous and also concurrent peripheral plasma samples of patients suffering from primary hyperaldosteronism; in two analyses of peripheral plasma from patients suffering from Cushing's syndrome due to an ectopic ACTH-producing tumour. It was possible, using the method, to predict from the adrenal venous results the site of the lesion in the 7 cases analysed. It is thought that the method may be of diagnostic value, also in helping to distinguish primary hyperaldosteronism due to an adenoma from that due to bilateral hyperplasia. Results from the two patients with Cushing's syndrome indicated yet again that high levels of ACTH cause gross elevation of DOC and corticosterone secretion and considerable disruption of electrolyte metabolism. The "multisteroid" approach has advantages over individual steroid estimation methods in that it is possible to monitor the secretory pattern of adrenocorticoids in investigation of both normal adrenal physiology and abnormal disease processes. It is thought that this type of measurement may be of particular value in research into causes of hypertension, where many factors are interrelated.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: R MS Smellie
• Keywords: Pharmacology, Analytical chemistry
• Date of Award: 1976
• Depositing User: Enlighten Team
• Unique ID: glathesis:1976-72283
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 24 May 2019 15:12
• Last Modified: 24 May 2019 15:12
• URI: https://theses.gla.ac.uk/id/eprint/72283