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SUMMARY
Differential solvent extraction was substituted for chromatography in the separation of the 17-oxosteroids formed by the treatment of urinary 17-hydroxycorticosteroids with sodium borohydride and with sodium periodate. Aetiocholanolone was extracted with iso-pentane which does not extract 11-hydroxyaetiocholanolone; 11-hydroxyaetiocholanolone can then be extracted with ether. The 17-oxosteroid content of each extract was determined using the Zimmermann reaction.
Evidence for the effectiveness of the separation of the two fractions is presented. The method is discussed in terms of its reliability and clinical usefulness particularly with respect to the metyrapone test.
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SUMMARY
Concentration and specific activity of plasma cortisol were measured for 4 h after the intravenous injection of 10 μCi [1,2-3H]cortisol into 14 normal men. Of these subjects four were resting controls; four exercised at a high work load for 1 h; four exercised at a low work load for 1 h and two received infusions of unlabelled cortisol, all beginning 1 h after the administration of [1,2-3H]cortisol.
In the high work load group plasma cortisol had increased by 12·2 ± 6·3 μg/100 ml at the 60th minute of exercise. In this group the half-life of [3H]cortisol was 31·5 ± 5·3 (s.d.) min in contrast to 74·5 ± 8·3 min for the resting controls (P < 0·001).
In the light exercise group plasma cortisol concentration tended to fall, but due to large intersubject differences this was not statistically significant. In this group the half life (t½) of [3H]cortisol was 43·8 ± 3·9 min which was also significantly different from that of the resting controls (P < 0·001).
Specific activity of plasma cortisol fell rapidly (mean t½ = 15 min) during 1 h of heavy exercise, and continued to fall to a nadir 10–30 min after exercise had ceased, finally reaching a value some 60% above the nadir 1·5–2·0 h after exercise had ceased. A similar, although exaggerated, pattern was observed in the two resting subjects into whom 5 and 4 mg respectively, of unlabelled cortisol were infused. In contrast, in the light exercise group cortisol specific activity changed only slowly (mean t½ = 151 min) but continued to fall after exercise.
In the light exercise group, during the latter part of exercise and during the first hour after exercise, the ratio [3H]cortisone: [3H]cortisol in plasma was significantly higher than the corresponding values for the resting group (P < 0·05). Even higher values for this ratio were obtained for some of the heavy exercise subjects but due to wide scatter the group was not statistically significantly different from the resting group.
These results suggest that exercise itself increases the rate of uptake of cortisol by peripheral tissues and that when the work load exceeds a critical level stimulation of the adrenal cortex results in a massive secretion of cortisol which is sufficient to raise the plasma level which in turn promotes further ingress of cortisol into the tissues. After exercise at a high work load a return of cortisol from the tissues to the plasma can be detected.
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SUMMARY
A method for the analysis of urinary 17-hydroxycorticosteroids is described. The urinary steroids are submitted, in situ, to sodium borohydride reduction, sodium periodate oxidation and mild alkaline hydrolysis. The generated 17-ketosteroids are separated by partition chromatography into 11-deoxy and 11-oxy fractions which are separately estimated by the Zimmermann reaction. By this method it is possible to estimate the urinary metabolites of cortisol without interference by corticosteroids not oxygenated at C-11.
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MRC Environmental Physiology Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT and * Army Personnel Research Establishment, R.A.E. Farnborough, Hampshire
(Received 22 February 1975)
It has been shown that passive heating first leads to a decrease in the level of plasma cortisol, but when body temperature exceeds about 38·3 °C increased cortisol secretion reverses this trend, and the level of plasma cortisol rises (Collins, Few, Forward & Giec, 1969). Also Okada, Matsuoka & Kumahara (1972) have shown that mild hyperthermia leads to a rise in the level of plasma growth hormone (GH). However, the relationship between GH secretion and cortisol secretion in more severe hyperthermia has not been studied. We have studied changes in plasma GH and cortisol in eight men whose body temperature was raised rapidly by mild exercise in a hot environment.
Eight healthy male subjects aged between 18 and 29 years were
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The steroid 11-oxygenation index (i.e. the ratio of the urinary metabolites of cortisol precursors to those of cortisol) has been used by Hill (1960) and by Edwards, Makin & Barratt (1964) in the diagnosis of congenital adrenal hyperplasia. Both showed that any circadian variations in the index were small compared with the gross abnormalities encountered in this condition. In the course of physiological studies on temperature and renal excretory circadian rhythms we have observed a small but definite circadian variation in the steroid 11-oxygenation index in normal men.
Six male subjects (ages ranging from 21 to 55 yr.) followed a routine consisting of rest, light activity, feeding and drinking, which was repeated every 90 min. during a 27 hr. experiment. Urine was collected for 3 hr. periods and the 11-deoxy and 11-oxy 17-hydroxycorticosteroids (11-deoxy and 11-oxy 17-OHCS) were separately estimated (Few, 1968) in each sample. The steroid 11-oxygenation index was
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MRC Environmental Physiology Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT
(Received 8 April 1976)
Reports on the changes in plasma cortisol level induced by exercise are uncommon, but contradictory. We have previously shown that exercise for 1 h, only leads to a rise in plasma cortisol concentration if the work load exceeds about 60% of the subject's maximal aerobic power (V̄O2, max); that is if his oxygen consumption exceeds 60% of the maximum of which he is capable (Davies & Few, 1973). We have now obtained further evidence of the importance of relative work load (% V̄O2, max) in eliciting an adrenocortical response to exercise, by comparing the changes in plasma cortisol at a given work load under normoxic and hypoxic conditions. The hypoxic condition was breathing 13% oxygen which was expected to reduce V̄O2, max by about 25% (Davies & Sargeant, 1974).
Five
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MRC Environmental Physiology Unit, London School of Hygiene & Tropical Medicine, Keppel Street, London, WC1E 7HT
(Received 10 September 1976)
Exercise for 1 h, at work loads exceeding about 60% of a subject's maximum aerobic power (V̄O 2, max), generally leads to a rise in plasma cortisol concentration (Davies & Few, 1973). The observed rise in plasma cortisol level is the net effect of increases in both the rate of secretion, and the rate of removal from the plasma, of cortisol (Few, 1974). Occasionally exercise at work loads exceeding 70% V̄O 2, max fail to elicit a significant rise in plasma cortisol level. Such a result could be due either to a failure to increase the rate of cortisol secretion or to an unusually rapid rate of cortisol removal.
In an attempt to resolve this ambiguity we have analysed data from ten experiments on normal men who exercised for 1 h at
