The production and characterisation of antisera to 17-hydroxyprogesterone

Plasma 17-hydroxyprogesterone determination with two commercial immunoassays

Plasma 17-hydroxyprogesterone (17-OH-P) was determined by two commercially available immunoassay kits, a radioimmunoassay (RIA) (OHP-CT, CIS) and an enzyme-immunoassay (EIA) (Serozyme 17 alpha-OH-progesterone, Serono). The determination by RIA was performed according to two procedures, directly on plasma or on a crude plasma extract, whereas that by EIA used only the second procedure. These determinations were carried out in 27 infants below 1 year of age and in 33 women in the follicular phase of the menstrual cycle. The results were compared to those obtained by an in-home RIA (RIA-FRH) which includes an extraction step followed by chromatography on Sephadex LH 20 column. The levels observed were overestimated by both kits. In infants, interference from 17-hydroxy-pregnenolone (17-OH-5P) sulfate occurred when the RIA (CIS) kit was used directly on plasma samples. Using plasma extracts, 17-OH-5P interfered with EIA (Serono) in the infant group and with the RIA (CIS) in the second group. The two kits do not appear to be adequate for 17-OH-P determination at least in infants and in women in the follicular phase of the menstrual cycle.

Catalytic antibody activity elicited by active immunisation. Evidence for natural variation involving preferential stabilization of the transition state

1. The hydrolytic activity of IgG purified from (a) 13 samples of ovine antiserum collected from three animals during a two-year immunisation programme using a phosphate immunogen (comprising the amide conjugate bonded through the carboxy group of 4-nitrophenyl 4-carboxymethylphenyl hydrogen phosphate and amino groups of keyhole-limpet haemocyanin) and (b) a sample of ovine antiserum collected from another animal during an 18-week immunisation programme using an analogous sulphone immunogen (comprising the amide conjugate bonded through the amino group of 4-nitrobenzyl, 4-(4-aminobutoxy)benzyl sulphone and carboxyl groups of keyhole-limpet haemocyanin) were evaluated kinetically by using 4-nitrophenyl 4-(3-aza-2-oxoheptyl)phenyl carbonate and 4-nitrophenyl 4-(2-hydroxyethoxy)phenyl carbonate as substrates. 2. Catalytic activity was found in all 13 samples of anti-phosphate IgG but was absent in the sample of anti-sulphone IgG as well as in all samples of IgG isolated from the serum of non-immunised animals. These findings, taken together with the lack of catalytic activity of the anti-phosphate IgG towards the 2-nitrophenyl 4-(3-aza-2-oxoheptyl)phenyl carbonate, compel the view that the catalytic activity of the anti-phosphate IgG preparation is entirely antibody-mediated and is not due to contaminant hydrolytic enzymes. The fact that catalytic activity was found in all 13 samples of the anti-phosphate IgG provides the first evidence that it is possible, as a routine, to elicit a catalytic antibody response in a host animal via active immunisation. 3. The nature of the, albeit small, variation in the catalytic characteristics of the anti-phosphate IgG (increase in both kcat, the catalytic rate constant calculated as V/2[IgG] and kcat/Km, the apparent second-order rate constant for the overall catalysed conversion of substrate to products, with increase in Km suggests simultaneous improvement in transition state binding and deterioration in substrate binding as predicted from immunogen design and the postulated general mechanistic basis of antibody catalysis. 4. This interpretation is supported by the difference in the values of the dissociation constant Ki for the competitive inhibition by the transition-state analogue 4-methylphenyl 4-nitrophenyl hydrogen phosphate of reactions catalysed by two representative anti-phosphate IgG samples: for the catalysis with Km = 4.5 microM, Ki = 9 nM and for that with Km = 1.3 microM, Ki = 80 nM.(ABSTRACT TRUNCATED AT 400 WORDS)

Steroid hormone abnormalities in women with severe idiopathic constipation

Patients with severe idiopathic constipation are almost exclusively women of reproductive age. To investigate the possibility of a sex hormone abnormality in this condition, we have compared a range of sex hormones during the follicular and luteal phases of the menstrual cycle in 23 healthy women (mean age 33 years) with those in 26 patients with severe idiopathic constipation (mean age 32 years, spontaneous bowel frequency less than one per week). In the patients there was a reduction in the follicular phase of progesterone (4.5 v 4 nmol/l, p = 0.006, median value, controls v patients), 17 hydroxyprogesterone (9.7 v 5.8 nmol/l, p = 0.01), cortisol (387 v 245 nmol/l, p = 0.008), testosterone (2.3 v 1.8 nmol/l, p less than 0.001), androstenedione (10.3 v 8.4 nmol/l, p = 0.02), and dehydroepiandrosterone sulphate (5.1 v 3.0 mumol/l, p = 0.03). In the luteal phase there was a reduction of oestradiol (483 v 350 pmol/l, p = 0.015), cortisol (322 v 242 nmol/l, p = 0.047), and testosterone (2.4 v 1.7 nmol/l, p = 0.003). The concentrations of sex hormone binding globulin, prolactin, luteinising hormone, and follicle stimulating hormone were not significantly different in either phase of the cycle. Women with severe idiopathic constipation have a consistent reduction in steroid hormones.

Development of a direct [125I]radioimmunoassay for serum levels of 17-hydroxyprogesterone

We describe a direct, rapid, sensitive and highly specific radioimmunoassay for determining serum levels of 17-hydroxyprogesterone. It is based on the use of highly specific sheep antiserum, 125I-labelled tracer, dextran-coated charcoal to separate the antibody bound and free fractions, and sodium salicylate to eliminate interference from endogenous binding proteins in serum. Intra- and interassay coefficients of variation are less than 8% and recovery is satisfactory. Sensitivity is 3.5 fmol per assay tube (0.14 nmol/l). Results correlate closely with those of an established technique using 3H-labelled steroid after initial solvent extraction and column chromatography of samples (y = 1.02x - 0.16; r = 0.998). The values found for serum from normal adult subjects ranged from 1.0 to 12.1 nmol/l while those from treated and untreated patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency were 1.4-18.4 and 27.3-650 nmol/l, respectively.

Comparison of separation techniques in radioimmunoassays for 17-hydroxyprogesterone

Separation techniques have been studied in the development of a direct radioimmunoassay to determine levels of 17-hydroxyprogesterone in serum. The same highly specific sheep antiserum was used throughout, together with the same amount of 125I-labelled 17-hydroxyprogesterone to which was added sodium salicylate to eliminate interference by endogenous binding proteins in serum samples. In one approach, dextran-coated charcoal was employed to adsorb the free fraction and, in another, the antibodies were covalently coupled to magnetisable particles. The antiserum was also adsorbed to assay tubes either directly or indirectly through second (double) antibodies. Analytical recovery and specificity were similar irrespective of the separation technique as was the correlation with results obtained by a reference assay. Levels of 17-hydroxyprogesterone in sera from normal adults and from treated and untreated patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency were also similar. However, the assay employing dextran-coated charcoal for separation showed the best precision and resulted in the greatest sensitivity, while the use of antibodies adsorbed indirectly to assay tubes was superior in terms of practicability.

Development of a direct fluoroimmunoassay for serum levels of 17-hydroxyprogesterone

A direct, rapid and highly specific fluoroimmunoassay for determining serum levels of 17-hydroxyprogesterone has been developed. It is based on the use of a sheep antiserum covalently coupled to magnetisable particles and fluorescein-labelled steroid. Sodium salicylate is employed to eliminate interference from endogenous binding proteins in serum. The sensitivity of 0.5 nmol/L is adequate for clinical purposes. Analytical recovery, linearity and precision are satisfactory and the results obtained correlate closely with those of an established radioimmuno-assay using 3H-labelled steroid and the same antiserum after initial sample extraction and chromatography. The values found for serum from normal adult subjects ranged from 1.0 to 12.6 nmol/L while those from treated and untreated patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency were 1.5 to 19.0 and 28.0 to 655 nmol/L, respectively.