We describe a direct radioimmunoassay for cortisol in 10-microliter volumes of parotid saliva or whole saliva. Binding proteins are absent from these fluids, as demonstrated by the excellent correlation between results for samples assayed directly and by a comparison procedure involving extraction with 1,2-dichloroethane. The direct assay is specific, precise, and had a lower limit of sensitivity of 4 pg per assay tube. Comparison of cortisol concentrations in plasma, parotid saliva, and whole saliva in persons undergoing investigations for assessing adrenal function, including stimulation with cosyntropin (Synacthen) and suppression with dexamethasone, indicated that changes in plasma cortisol concentration were accurately and immediately reflected in saliva from either the parotidgland or whole saliva. A marked circadian rhythm has also been demonstrated for cortisol in parotid-gland saliva and whole saliva. We had to modify the 1,2-dichloroethane extraction procedure for accurate determination of cortisol in parotid saliva and whole saliva of patients undergoing treatment with metyrapone.
The effect of anticonvulsant therapy on early morning concentration of cortisol in saliva and plasma was assessed in a group of epileptic patients receiving regular phenytoin medication and the results compared with those obtained from a group of normal subjects not receiving drug therapy. Values of cortisol in matched samples of plasma (331 +/‐ 23 nmol l‐1, mean +/‐ s.e. mean, n = 6) and saliva (11.4 +/‐ 0.9 nmol l‐1, mean +/‐ s.e. mean, n = 9) provided by epileptics did not differ significantly from those in the plasma (334 +/‐ 41 nmol l‐1, mean +/‐ s.e. mean) and saliva (12.0 +/‐ 2.0 nmol‐1, mean +/‐ s.e. mean) of healthy volunteers (n = 12). Six anticonvulsant‐treated epileptics, together with six age and sex matched normal volunteers, each received intravenous dexamethasone (1 mg h‐1) to determine the half‐life of cortisol in plasma and saliva. In the anticonvulsant‐ treated group, the half‐life of cortisol in plasma (73 +/‐ 5 min, mean +/‐ s.e. mean) and saliva (83 +/‐ 5 min, mean +/‐ s.e. mean) was reduced significantly (P less than 0.01 plasma, P less than 0.05 saliva) from that observed in healthy volunteers. In patients, the half life of cortisol and antipyrine showed a significant correlation (r2 = 0.75, P less than 0.05 plasma, r2 = 0.71, P less than 0.05 saliva). The antipyrine half‐life in saliva was reduced significantly (P less than 0.02) and the antipyrine clearance rate, increased significantly (P less than 0.005) in the treated epileptic group, reflecting drug‐ induced microsomal enzyme production.(ABSTRACT TRUNCATED AT 250 WORDS)
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