transport of docosahexaenoic acid (22:6 n-3, DHA) by GDM ( Herrera & Ortega-Senovilla 2010 , Leveille et al. 2018 ), likely as a consequence of alterations in fatty acids (FA) transport proteins related to phospholipids transfer such as the major
Samples from three early human placentae were incubated with [4-14C]-dehydroepiandrosterone (DHA). It was found that [4-14C]DHA was transformed into 7-oxygenated derivatives in yields decreasing in the order: 7-oxo-DHA > 7β-hydroxy-DHA > 7α-hydroxy-DHA. These products were only slowly transformed into other derivatives.
The secretion of dehydroepiandrosterone (DHA) and its sulphate (DHAS) was examined by measuring their concentrations in adrenal venous, gonadal venous, and peripheral venous plasma. Both steroids were secreted by the adrenal cortex and the rate of DHA secretion was higher than that of DHAS in seven out of eight subjects. Adrenocorticotrophin (ACTH) caused an increase in DHA and DHAS secretion by 15–30 min after administration. When ACTH was infused for 8 h, peripheral DHA concentrations increased at 2 h and decreased subsequently in five out of eight subjects suggesting depletion of substrate or cofactors for this biosynthetic pathway.
Gonadal secretion of DHA was present in each subject (eight women and two men) but DHAS secretion could not be demonstrated. Exogenous human chorionic gonadotrophin (HCG) caused an increase in plasma DHA. Examination of the diurnal variation of plasma DHA concentrations revealed a 40% decrease from 08.00 to 20.00 h.
The role of pregnenolone sulphate in adrenal steroid biosynthesis and the ability of the human adrenal gland to synthesize and secrete dehydroepiandrosterone (DHA) and dehydroepiandrosterone sulphate (DHA sulphate) was investigated. The presence of pregnenolone sulphate and DHA sulphate was demonstrated by measuring their concentrations in human adrenal tissue. Pregnenolone sulphate was metabolized in vitro mainly to free steroids, including DHA and cortisol, as well as directly to DHA sulphate in some cases. Similar results were obtained upon perfusion of the adrenal gland in situ with [14C]pregnenolone and [3H]pregnenolone sulphate as the substrates and isolating the metabolites from the adrenal venous blood. Dehydroepiandrosterone sulphate was derived mainly from the sulphation of free DHA. The hydrolysis of DHA sulphate did not appear to make a significant contribution to the amounts of DHA synthesized under these conditions.
The adrenal secretion of DHA and DHA sulphate by eight patients undergoing adrenalectomy was determined by measuring the concentrations of these compounds in samples of adrenal and peripheral venous blood taken simultaneously. In one patient secretion of DHA and DHA sulphate was equivalent whilst in the remainder there was much greater secretion of DHA.
It has been shown (Julesz, Faredin & Tóth, 1966) that the human male and female axillary and pubic hair contains large amounts of dehydroepiandrosterone (DHA) and that a significant part of this steroid is present in the form of its sulphate ester (DHA-sulphate) (Tóth, Faredin & Julesz, 1967). Gallegos & Berliner (1967) recently described the conjugation in vitro of DHA to DHA-sulphate (DHA-S) by human male abdominal skin slices. The present communication deals with the metabolism of DHA in female skin.
Normal abdominal skin (dermis and epidermis) was obtained from women during appendectomy. The skin sample (1 g.) was chopped with scissors into cubes of 1–2 mm. diameter and incubated with 1,122,880 disintegrations/min. (d.p.m.) [4-14C]DHA (Radiochemical Centre, Amersham, sp.act. 7·8 μc/μm) in 10 ml. Krebs—Ringer—phosphate solution, pH = 7.4 (containing 200 mg. glucose/100 ml., 10−3m-NAD, 10−3m-NADP and 10−3m-ATP)
Concentrations of 5-androstene-3β, 17β-diol (androstenediol), dehydroepiandrosterone (DHA) and DHA sulphate (DHAS) were measured in endometrium and plasma from normal premenopausal and perimenopausal women (average ages 37 and 48 years respectively) at different stages of the menstrual cycle. Plasma levels did not vary with the stage of the cycle for any of the three steroids. Mean plasma levels of androstenediol ranged between 2·03 and 2·92 nmol/l for premenopausal women and 1·38 and 1·58 nmol/l for perimenopausal women while mean concentrations of DHA were 20·80–36·41 nmol/l (premenopausal women) and 13·87–19·07 nmol/l (perimenopausal women). The values for DHAS were more variable and ranged between 3·20 and 4·56 and 2·94 and 4·25 μmol/l for pre- and perimenopausal women respectively.
In premenopausal women endometrial tissue concentrations of androstenediol and DHA increased three to fourfold in the secretory phase while no increase was observed in DHAS. There was a similar increase in androstenediol but not DHA or DHAS during the secretory phase for perimenopausal women. A significant positive correlation was found for tissue androstenediol and DHA in both groups of women but the relationship between DHAS and the other androgens was significant only for perimenopausal women.
We suggest that the increase in androstenediol and DHA concentrations could be due to an increase in a receptor or binding protein, possibly progesterone dependent, present in secretory phase endometrium.
The effects of human pituitary extracts upon steroid biosynthesis by pieces of human adrenal tissue incubated in Krebs—Ringer bicarbonate buffer have been studied. Experiments with both adult and foetal adrenal tissue have been carried out. Radioactive precursor (either [7-3H]pregnenolone or [4-14C] progesterone) was added to each incubation vessel and the synthesis of radioactively labelled products was estimated by reverse isotope dilution. Individual steroids were characterized by paper and thin-layer chromatography; the radiochemical purity of cortisol, androstenedione, dehydroepiandrostenedione (DHA) and DHA sulphate was established following derivative formation. There was no consistent effect of the pituitary preparations upon the biosynthesis of cortisol, DHA or DHA sulphate, nor upon the ratio of cortisol to the combined production of DHA and DHA sulphate. However, the production of androstenedione from both [7-3H]pregnenolone and [4-14C]progesterone was significantly increased in the presence of pituitary and gonadotrophic preparations.
The pathways of dehydroepiandrosterone sulphate (DHAS) biosynthesis in adrenal glands from the human previable foetus have been investigated by incubating pregnenolone, 17 α-hydroxypregnenolone and pregnenolone sulphate with homogenates of this tissue for different periods of time. The steroids formed were identified and measured by reverse isotope dilution or by gas—liquid chromatography and mass spectrometry of their derivatives. The results obtained are consistent with a main pathway from pregnenolone to DHAS via non-sulphated intermediates, i.e. 17 α-hydroxypregnenolone and DHA. The rate of pregnenolone sulphate metabolism to DHAS via 17 α-hydroxypregnenolone sulphate was found to be very slow compared with the rapid metabolism of pregnenolone to DHAS. These results are discussed in relation to the availability and nature of DHAS precursors in vivo.
A method for the measurement of dehydroepiandrosterone (DHA) and of its sulphate (DHAS) in human peripheral plasma is described and evaluated. After isolation of DHA from the sample the steroid is oxidized to 4-androstene-3,6,17-trione, which is measured with an electron capture detector after gas—liquid chromatography. It is possible to detect 100 pg 4-androstene-3,6,17-trione. The smallest amount of DHA per sample that can be distinguished from zero is approximately 4 ng, when recovery (27·9 ± 8·8%) and method blank (0·23 ± 0·38 ng) are taken into account. The oxidation to 4-ene-3,6-diones is specific for steroidal 5-en-3-ols. Specificity for DHA is ensured by several chromatographic steps. Repeated estimation of 10 ng DHA gave a mean value of 9·6 ± 1·45 (s.d.) ng (n = 35). Mean concentrations and their standard deviations for DHA and DHAS in peripheral plasma from 18 individuals were 0·50 ± 0·25 and 78 ± 40 μg/100 ml, respectively, at 08.30 h and 0·32 ± 0·17 and 84 ± 34 μg/100 ml, respectively, at 17.00 h of the same day. Levels of plasma cortisol in the same plasma samples estimated with a competitive protein-binding method were 16·7 ± 1·8 and 11·9 ± 3·8 μg/100 ml, respectively. No significant differences between the sexes were observed by any of the three assays. The mean values of the plasma concentrations of cortisol and DHA in the morning were significantly higher than those in the evening (P < 0·001 and P < 0·005, respectively). In contrast, the mean value of the plasma levels of DHAS in the morning was significantly lower than that in the evening (P < 0·025).
The metabolism of [3H]pregnenolone and [3H]dehydroepiandrosterone ([3H]DHA) by tissue from the separated zones and whole adrenal glands from newborn anencephalic infants was investigated.
Pregnenolone was metabolized by the whole gland homogenates mainly to pregnenolone sulphate and unconjugated 17α-hydroxypregnenolone and also to small amounts of DHA and dehydroepiandrosterone sulphate (DHAS). DHA was metabolized by the whole gland homogenates mainly to androstenedione and DHAS and small amounts of 11β-hydroxyandrostenedione.
Adrenal gland tissue from a 42-week-old anencephalic infant containing three histologically distinct zones in the adult cortex in addition to residual foetal zone had sulphokinase, 17α-hydroxylase, 17–20 lyase and 3β-hydroxy-steroid dehydrogenase/Δ4,5 unsaturated isomerase activity in each of these zones. These enzymes were also present in the adrenal adult zone of another anencephalic infant.
Omission of ATP from the incubation medium greatly reduced the conversion of DHA to DHAS in the homogenates and separated zones.
These results are discussed in relation to oestrogen biosynthesis in anencephaly and to foetal 4-en-3-oxosteroid synthesis in utero.