Genistein and daidzein modulate in vitro rat uterine contractile activity

The present study investigated the effect of genistein, daidzein and estradiol on in vitro rat uterine responsiveness to oxytocin (OT) and PGF(2)alpha or luprostiol (L). In a first experiment, animals were either sham-operated (SH; n=5), or ovariectomized (OVX; n=20) and orally treated for three months with either genistein (G; n=5; 10 microg/g BW/d) or daidzein (D; n=5; 10 microg/g BW/d) or 17 alpha-ethinylestradiol (E; n=5; 23 microg/kg BW/d) or untreated (OVX; n=5). At necropsy, the basal uterine tension was lower in OVX, G and D than in SH, the highest value being measured in E. Oxytocin (10(-12); 10(-11) M) or PGF(2)alpha (10(-12); 10(-9) M) induced an increase in SH, but not in OVX, E and G. In D, only the highest doses were efficient. In a second experiment, 20 intact animals were s.c. injected with either genistein (G; n=5; 10 microg/g BW) or daidzein (D; n=5; 10 microg/g BW) or estradiol benzoate (E; n=5; 23 microg/kg BW) or vehicle (C: controls; n=5), and killed 24 h later. In C and E, OT (10(-15) to 10(-10) M) or L (10(-12) to 10(-7) M) stimulated uterine contractile activity in a dose-dependent manner until a maximal level. On the opposite, in G and D, contractile agents (except the highest luprostiol doses) did not stimulate myometrium contractions. Moreover, radioligand binding assays showed that genistein or daidzein inhibited the specific binding of [(3)H] estradiol to the calf uterus estrogen receptor (ER). Therefore, it could be postulated that both genistein and daidzein might bind to the rat uterus ER, inducing either anti-estrogenic or very weak estrogenic effects (depending on the experimental conditions) on in vitro uterine responsiveness to OT and PGF(2)alpha or luprostiol.

Time-course of the change in blood pressure level in magnesium-deficient Wistar rats

The aim of the present study was to determine whether a severely Mg-deficient diet can modify blood pressure in rats and whether these alterations in blood pressure are associated with a change in in vivo cardiovascular reactivity, alteration in plasma lipids and modification of the production of hormones involved in blood pressure regulation. Weanling male Wistar rats were pair-fed for 40 weeks with control (960 mg Mg/kg) and Mg-deficient (80 mg Mg/kg) diets. At 2 weeks, blood pressure was lower in Mg-deficient rats, while heart rate was greater than in controls. Mg-deficiency-induced hypotension was transitory and the administration of antihistamine agents inhibited the appearance of this hypotensive phase, suggesting that histamine may play a role in lowering blood pressure. Until 15 weeks, blood pressures were similar for control and Mg-deficient rats. Thereafter, blood pressure rose gradually until the end of the experiment in Mg-deficient rats. Heart rate remained higher in hypertensive Mg-deficient rats. After 21 weeks, in vivo cardiovascular reactivity to noradrenaline was lower and reactivity to angiotensin II was unchanged in hypertensive Mg-deficient rats. At 2 and 21 weeks, hypomagnesaemia was accompanied by higher plasma levels of Ca, triacylglycerols and cholesterol. Plasma renin activity was higher at week 2, whereas levels of plasma angiotensin converting enzyme were lower at 2 and 21 weeks in Mg-deficient rats. The plasma aldosterone level was higher at 2 and 21 weeks while the vasopressin level did not change. Plasma corticosterone levels were lower at 2 weeks and higher at 21 weeks. It is concluded that Mg deficiency induced a transitory hypotension followed by a sustained hypertension in rats. The release of vasodilator inflammatory agents may contribute to the early hypotension. The hypertensive phase may be explained by the increased sympathetic nervous activity induced by Mg deficiency even though the contribution of several hormonal systems implicated in blood pressure regulation remains to be elucidated.

Cytokine modulation by PX differently affects specific acute phase proteins during sepsis in rats

To explore the regulation of the acute phase response in vivo, the effects of pentoxifylline (PX) treatment (100 mg/kg ip 1 h before infection) were investigated in infected and pair-fed rats 2 and 6 days after an intravenous injection of live bacteria (Escherichia coli). PX treatment prevented the increase in plasma tumor necrosis factor (TNF)-alpha (peak 1.5 h after the infection) and resulted in an 84 and 61% inhibition of plasma interleukin (IL)-1beta and IL-6, respectively (peaks at 3 h). Plasma corticosterone kinetics were not modified by the treatment. Infection increased alpha1-acid glycoprotein (AGP), alpha2-macroglobulin (A2M), and fibrinogen plasma concentrations and decreased albumin levels. PX significantly reduced AGP plasma concentration as early as day 2 in infected animals but reduced A2M and fibrinogen plasma levels only at day 6. The treatment had no effect on the albumin plasma concentration. Hepatic AGP and fibrinogen mRNA levels increased in infected rats, whereas those of A2M were unchanged and those of albumin were decreased. Two days after infection, AGP and fibrinogen mRNA levels were reduced in treated infected animals. PX was ineffective in modifying those of A2M and albumin. These data demonstrate, in vivo, that different acute phase proteins are individually regulated in sepsis. The in vivo effects of PX treatment support the hypothesis that TNF-alpha plays an important role in the regulation of AGP production, whereas other factors seem to be involved in the regulation of A2M, fibrinogen, and albumin expression.

Effects of corticotrophin-releasing factor and vasopressin on plasma adrenocorticotrophin molecular forms, aldosterone and corticosterone in young and adult rats and rabbits

Synthetic ovine corticotrophin-releasing factor (CRF) and arginine vasopressin (AVP) were injected alone or in combination (for each peptide 1 microgram/kg body weight) in 7-day-old and adult rats and rabbits. Fifteen minutes after the interscapulary injection, blood was collected for plasma adrenocorticotrophin (ACTH), corticosterone and aldosterone evaluation by RIA. The different circulating forms of ACTH were isolated by Sephadex G50 column chromatography with 1% formic acid and measured by RIA using 1-24 ACTH as standard. Such experiments were previously described in lambs and guinea-pigs using the same schedule. In young and adult rabbits the predominant circulating IR-ACTH form was 'big' ACTH; after stimulation with CRF, AVP or CRF + AVP the 'intermediate' IR-ACTH was greatly increased in adults, but no change was observed in young rabbits. In young and adult rats the predominant circulating form was "intermediate' ACTH in control and injected animals; ACTH increased after CRF alone or in combination with AVP, but not after AVP alone. In both species the 'intermediate' forms of IR-ACTH were not eluted at the same time by chromatography, and calculated molecular weights were different: 14500 in rats and 9500 in rabbits. Plasma corticosterone and aldosterone were increased in rat and rabbit adults after CRF and AVP; however, they remained unchanged in young rabbits and slightly increased only after CRF in young rats in which corticosterone remained at a very low concentration compared with that in adults. Hence, the pituitary-adrenal axis of 7-day-old rabbits and rats in less reactive than that of sheep and guinea-pig of the same age.

Distribution and metabolism patterns of plasma 7S- and beta-NGF in the adult male rat

There is a great deal of controversy on the existence of NGF in body fluids and tissues. To date it remains unknown whether this peptide accumulates preferentially at significant levels in different organs. Thus we undertook the evaluation of kinetic parameters of the disappearance of blood of 125I-7S-NGF and 125I-beta-NGF after intravenous injection in male adult rats. Our results indicate that the plasma half-life of 125I-7S-NGF is approximately twice as long as for 125I-beta-NGF (respectively 61.7 +/- 11.7 min and 36.3 +/- 2.2 min) while the distribution volume is not significantly different between both peptides. Furthermore, the uptake of radioactive NGF by different tissues seems very low as shown by 125I-7S-NGF and 125I-beta-NGF content of the sampled organs compared to the plasma concentration at the same time. These results indicate that the tissue uptake of circulating 7S and beta-NGF is very low in the adult rat. Thus in these animals NGF did not cross the blood-brain barrier and did not accumulate in peripheral organs which are known to contain subsequent amounts of this peptide. This lack of deposition might be due to a binding with plasma proteins (probably alpha 2-macroglobulin).

Endocrine and hemodynamic responses to dopamine infusion in the guinea-pig: effects of ACE inhibition with perindopril

The effects of dopamine on plasma renin-angiotensin-aldosterone system vasopressin levels and blood pressure were studied in anesthetized guinea-pig. The inhibition of the angiotensin converting enzyme with perindopril permitted assessment of the role of the renin-angiotensin system. In perindopril-treated guinea-pigs, the activity of angiotensin-converting enzyme was decreased by 90% with simultaneous increases in plasma renin activity and angiotensin I concentration; aldosterone and vasopressin levels, blood pressure and heart rate were not modified. Dopamine depressed mean arterial pressure by 30% and increased heart rate (8%) in controls. Dopamine infusion did not affect either plasma renin activity or angiotensin I concentration or angiotensin-converting enzyme activity in control animals. But in perindopril pretreated animals it further increased plasma renin activity (88%) and angiotensin I concentration (35%). Finally, in controls, dopamine infusion increased plasma vasopressin concentrations (91%) whereas this increase did not occur in perindopril treated animals.

Magnesium and blood pressure. I. Animal studies

The relationship between experimental magnesium deficiency and blood pressure is complex and still the subject of much debate. The effect of Mg deficiency and blood pressure in Wistar rats receiving a Mg deficient diet (0.080 g/kg) for 40 weeks was examined. Deficient rats, when compared to controls, showed an initial transitory phase of hypotension, followed by normalization of blood pressure and then hypertension beginning after 15 weeks on the deficient diet. During the whole experimental period, heart rate was significantly increased in deficient rats as compared to controls. The fact that hypotension resulting from Mg deficiency of short duration can be inhibited by antihistamines and by indomethacin suggests that various mediators seen during the inflammatory period of Mg deficiency could be involved. Mg deficiency of long duration was accompanied by hypertension. When Mg-deficient rats received the control diet for a period of 3 weeks, Mg supplementation only partially corrected the hypertension. The hypertension was not a consequence of stimulation of the renin-angiotensin system since the plasma renin activity was not modified and ACE activity was reduced. These deficient rats showed a significantly lower vasopressor response to noradrenaline than control rats. Several factors such as increase in collagen, changes in elastin and arterial elasticity, total lipid content, and calcifications may account for the hyporesponsiveness to contractile agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Parathyroid hormone-related peptide inhibits oxytocin-induced rat uterine contractions in vitro

Synthetic human parathyroid hormone-related peptide (hPTHrP)-(1-34) fragment was compared with parathyroid hormone (bovine sequence, 1-34; bPTH-(1-34) for inhibiting oxytocin or prostaglandin F2 alpha (PGF2 alpha)-induced contractions on rat uterus in vitro. bPTH exhibited a potent (ED50 = 7 x 10(-9) M) inhibition on oxytocin-induced contractions. Both bPTH-(1-34) and hPTHrP-(1-34) were devoided of any significant effect upon PGF2 alpha-induced uterine contractions. Human PTHrP also inhibited oxytocin-induced uterine contractions (ED50 = 77 x 10(-9) M) and this effect, like that of bPTH, was dose dependent. Human PTHrP-(140-173) fragment had no significant effect on oxytocin-induced uterine contractions. The inhibitory effect of hPTHrP-(1-34) disappeared after pretreatment with [Tyr]34-bPTH-(7-34)-NH2, a competitive reversible antagonist of bPTH-(1-34). Thus PTHrP might be involved in the control of myometrial activity.

Cardiovascular and hormonal responses to ANP infusion in the guinea-pig: effects of angiotensin-converting enzyme inhibition with perindopril

In the guinea-pig, perindopril inhibited plasma angiotensin converting enzyme (ACE) by 90% when given orally at 2 mg/kg/day during 10 days. Mean blood pressure and plasma aldosterone, cortisol and vasopressin concentrations were not modified by this treatment, while plasma renin activity (PRA) and plasma angiotensin I concentrations increased significantly. The same parameters were studied using a constant intravenous 30 min-infusion of atrial natriuretic peptide (ANP) (0.1 micrograms.kg-1min-1). This dose of ANP infused to anesthetized guinea-pigs induced a significant decrease in mean blood pressure (about -20%) in control and in perindopril treated animals. In ANP infused animals, plasma aldosterone and cortisol concentrations decreased similarly in both groups by about -50%, whereas plasma vasopressin concentrations increased in controls (+169%) but not in perindopril treated guinea-pigs. An increase in PRA and plasma angiotensin I concentrations was observed in both groups after the infusion of ANP. Thus, when ANP demonstrated an potent hypotensive effect a concomitant increase in PRA occurred. The rise observed in vasopressin concentration in control animals was probably mediated by angiotensin II. The fall in plasma aldosterone and cortisol concentrations observed after ANP infusion demonstrated a direct potent action of ANP at the adrenal levels.

Lack of effect of perindopril on plasma and adrenal corticosteroids in the guinea pig during the estrous cycle and under contraceptive treatment

We studied changes in cortisol, aldosterone, progesterone, estrogens and cholesterol in cyclic female guinea-pigs and in animals under contraceptive, treated or not with an inhibitor of angiotensin converting enzyme (ACE): perindopril. Perindopril decreased ACE by 80% without affecting steroid profiles. Peak value for plasma progesterone occurred at meta-estrus and diestrus. It disappeared under contraceptive treatment. The very low levels of estrogens in the female guinea pig remained unchanged in all cases. Plasma cortisol concentrations were higher at pro-estrus and estrus whereas plasma aldosterone concentrations remained constant during the estrous cycle and under contraceptive treatment. Furthermore, aldosterone did not change under perindopril treatment despite the decrease of the activity of ACE. The contraceptive treatment decreased plasma cholesterol levels. Under perindopril treatment, this drop was amplified. No change was detected in adrenal steroid concentrations, except for progesterone which decreased under contraceptive treatment.

Pituitary and adrenal responses to ovine corticotropin releasing factor and vasopressin injected into young and adult guinea-pigs

Comparison of effects of synthetic ovine corticotropin releasing factor (oCRF), Arginine-Vasopressin (AVP) and the combination of both peptides have been tried in adult and 7-days-old guinea-pigs. On plasmas collected 15 min after interscapulary injection, cortisol, aldosterone and ACTH were measured. The different circulating forms of ACTH were isolated by Sephadex G50 column chromatography, with 1% formic acid and measured by radioimmunoassay. Thus, in the guinea-pig plasma, we detected three immunoreactive forms of ACTH: a "big" molecular form (Mr greater than 20000), an "intermediate" (Mr = 9500) and a "little" ACTH form (Mr = 4500) which was eluted in the same fractions as human 1-39 ACTH. In adult guinea-pigs, CRF increased total ACTH and the "intermediate" form and also plasma cortisol concentrations whereas AVP remained without significant effect excepted a rise in cortisol levels. Injected together, CRF and AVP enhanced plasma concentrations of total ACTH, of the three circulating forms and of cortisol. In 7-days-old guinea-pigs, both CRF and AVP increased plasma concentrations of total, of "intermediate" ACTH and of cortisol and aldosterone whereas the combination of both peptides enhanced dramatically plasma concentration of total ACTH suggesting a magnifying effect of AVP on CRF activity still more efficient in young than in adult guinea-pigs.

Sodium intake by pregnant cows and plasma aldosterone and cortisol concentrations in the fetus during late pregnancy

The purpose of this study was to evaluate the influence of maternal dietary Na intake on the plasma concentrations of aldosterone and cortisol in cows and their fetuses during late pregnancy. Seven cows received a diet with normal amounts of Na (25 g Na per cow/d) and seven others an Na-loaded diet (210 g Na per cow/d) during the last 40 d of gestation. Maternal and fetal blood samples were collected regularly during the last month of gestation through jugular vein puncture and cotyledonary artery indwelling catheters. Serum Na and K concentrations and plasma osmolalities increased, but concentrations of aldosterone decreased in maternal and fetal plasma when cows were fed the Na-loaded diet. Diets did not modify concentrations of cortisol in maternal and fetal plasma. Thus, an increase in Na intake by dams influenced concentration of Na and K in fetal plasma and fetal adrenal secretion of aldosterone.

A randomized comparison of early with conservative use of antihypertensive drugs in the management of pregnancy-induced hypertension

Two treatment strategies were compared in 155 women with pregnancy-induced hypertension who were also given comprehensive non-pharmacological care. The mean gestation at entry was 28 weeks. As long as the diastolic blood pressure (DBP) remained below 106 mmHg, oxprenolol, or oxprenolol plus dihydralazine, were given to the early treatment group, and matching placebos to the control group. Open antihypertensive treatment was provided for patients whose DBP rose above 105 mmHg. Proteinuria occurred in seven women in each group. In the early treatment group, 13 of the 78 women were delivered by caesarean section; the corresponding numbers in the control group were 27 of 76 (17 vs 36%, 95% confidence interval (CI) of difference: 5-33%); the sections included seven and 16 in the early treatment and control groups, respectively, for severe hypertension and/or fetal distress. There were five perinatal deaths, two in the early treatment group and three in the control group. Early treatment did not influence gestational age at birth or birthweight. Respiratory distress syndrome occurred in four infants in the early treated group and in 10 in the control group; 14 infants in the former group and 26 in the latter were in hospital for more than 10 days (18 vs 35%; 95% CI of difference 4-32%). These results indicate that early antihypertensive treatment with oxprenolol is safe for the fetus and newborn in pregnancy-induced hypertension, but has no advantage over non-pharmacological care in terms of fetal growth. However, it may prevent acute hypertension in late pregnancy and associated fetal distress, and thus reduce the number of caesarean sections.

Effects of neurotrophic stress on maternal metabolism and binding of plasma cortisol in late pregnant guinea-pigs and their fetuses

The maternal metabolic clearance rate (MCR) and the binding of cortisol in the plasma of fetus and mother were estimated 8 days before term in conscious pregnant guinea-pigs, control or subjected to a neurotrophic stress (they were immobilized for 3 h in a dark room in front of an intermittent luminous flash). The maternal MCR of cortisol dropped during pregnancy related to an increase in corticosteroid binding globulin (CBG) and the stress mimicked these changes with a decrease in MCR and a rise in CBG. The increase in cortisol concentrations occurring in the fetal plasma after maternal stress could be related to the increase in free cortisol in the stressed mother. Nevertheless, although the fetal CBG did not rise after maternal stress, the increase in free cortisol in the fetal plasma remained moderate, due to the numerous free sites of CBG and albumin for cortisol.

Diurnal pattern of plasma cortisol in preruminant calves fasted or fed different milk proteins

The objective was to clarify the possible role of meals in the nycthemeral evolution of cortisol and the influence of intestine absorption kinetic of nutrients. Preruminant calves were fed two kinds of diets, a conventional curdled milk and a milk that did not curdle in the abomasum. These calves were also fasted for 24 h. Blood was sampled regularly during a 24-h period under three different dietary situations. Daily mean plasma cortisol was lower in calves fed uncurdled milk than in those fed curdled milk or fasted. Diurnal changes in plasma cortisol were characterized in fed animals by sharp postprandial decreases; the morning meal induced a more intense decrease than the evening one, which was followed by a regular increase of cortisol concentrations overnight. Between meals, several peak values were detected at the same times in all animals with both kinds of meals. The postprandial decreases did not occur in fasted animals, and peak values could not be linked to those occurring when animals were fed. Thus, cortisol secretion by adrenals seemed to be influenced by nutrient intestinal absorption, whereas during fasting different mechanisms were involved.

Plasma concentrations of adrenocorticotropin-related peptides in lambs injected with ovine corticotropin releasing factor or vasopressin

Synthetic ovine corticotropin-releasing factor (oCRF) and arginine vasopressin (AVP) were intravenously injected each alone or in combination (each peptide: 1 microgram/kg body weight) in lambs on days 1, 3, 7 and 20 after birth. Plasma samples were collected just before and 10 and 30 min after injection. Plasma concentrations of cortisol and aldosterone were measured. Adrenocorticotropin (ACTH)-related peptides were isolated by Sephadex G50 column chromatography and measured by radioimmunoassay. Three different peaks with an ACTH immunoreactivity were found in lamb plasma: a "big" ACTH molecular form (Mr = 30,000), an "intermediate" (Mr = 8000) and a "little" (Mr = 4500). In 1 and 3 days-old lambs, both CRF and AVP increased preferentially "intermediate" ACTH. In 7 and 20 days-old lambs, an increase in "little" ACTH occurred after CRF whereas "intermediate" ACTH rose after AVP. The rise in plasma levels of different molecular forms of ACTH after stimulation by CRF or AVP could suggest that the biological pathway of ACTH synthesis, storage and release may occur in different intracellular pools or rather in different pituitary cells. Intermediate ACTH stimulated adrenal secretion of cortisol as soon as the first day of postnatal life and increased plasma aldosterone concentration in 7 and 20 day-old lambs. At these stages aldosterone level did not change after a rise in "little" ACTH.

Daily metabolism and hepatic balance studies of plasma cortisol and aldosterone in the preruminant calf

Intestinal and hepatic catabolism of cortisol and aldosterone were studied in the calf using blood samples from the mesenteric artery and portal and hepatic veins collected over 24 h, the hepatic blood flow being continuously recorded during this period. The total hepatic blood flow remained broadly constant over the 24 h, although meals were followed by decreasing flow in the portal vein and by increasing flow in the hepatic artery. The intestinal tract catabolizes cortisol as intensively as the liver (both 13% of cortisol reaching the organ). The part played by the gut and the liver in the catabolism of aldosterone were also equivalent (both 30% of aldosterone reaching the organ). This 24-h study demonstrated that a constant ratio existed between secretion and catabolism of cortisol while the hepatic balance of aldosterone seemed to be modified during the night.

Plasma concentrations of adrenocorticotropin-related peptides after corticotropin-releasing hormone and vasopressin injections in sheep

Ovine corticotropin-releasing hormone (1 micrograms/kg body weight) and arginine vasopressin (1 micrograms/kg) were injected iv in sheep, both separately and in combination. Plasma were sampled just before and 5, 15 and 30 min after the injection. Adrenocorticotropin-related peptides were isolated by Sephadex G-50 column chromatography and measured by RIA. Cortisol and aldosterone were determined on the same plasma samples. Three molecular forms of immunoreactive ACTH (IR-ACTH) were isolated: 'big' (greater than 20,000 mol wt), 'intermediate' (= 8000 mol wt) and 'little' (= 4500 mol wt). Following CRH injections, the three molecular forms of ACTH were enhanced, particularly the 'little' form, whereas 'intermediate' IR-ACTH was highly and specifically responsive to AVP. After a simultaneous injection of CRH and AVP, additive increases occurred for 'intermediate' and 'little' IR-ACTH. The release of different molecular forms of IR-ACTH after stimulation by CRH or AVP of corticotrope cells suggests that ACTH-related peptides could be stored in different intracellular pools or secreted by different pituitary cells.

Nycthemeral changes in plasma cortisol levels in preruminant calves with different milk proteins

Preruminant calves bearing indwelling catheters in the hepatic artery, the portal and the hepatic veins were fed with two kinds of diets, a conventional curdled milk diet and a milk diet which was uncurdled in the abomasum. Measurements of plasma cortisol in blood sampled regularly during the 24 hr of the day indicated that with curdled milk, cortisol concentrations were significantly higher than with uncurdled milk. Nycthemeral changes were characterized by high values before meals and by postprandial decreases. Between meals, several peak values were observed and in the night a regular increase occurred. With both kinds of meals, cortisol evolutions were similar though peak values were higher with the curdled milk.

Effects of prenatal maternal stress on the pituitary adrenocortical reactivity in guinea-pig pups

Seven days before term, pregnant guinea-pigs were subjected to a psychosomatic stress. Adrenocorticotrophin (ACTH), cortisol and aldosterone concentrations increased in maternal and fetal plasma immediately after stress. In the offspring born from prenatally-stressed mothers that were resubjected to stress, the increases in plasma ACTH and cortisol level were lower than in the control offspring. Plasma aldosterone levels increased after stress in 12 days-old pups but did not change neither in 50 days-old animals nor in 12 days-old guinea-pigs born of prenatally stressed mothers. Thus prenatal stress of mother resulted in lowered response of pituitary-adrenocortical axis of offspring subjected to stress.

Plasma adrenocorticotrophin, cortisol and aldosterone responses to ovine corticotrophin-releasing factor and vasopressin in sheep

Ovine corticotrophin-releasing factor (oCRF) (1 microgram/kg) and arginine vasopressin (AVP) (1 microgram/kg) were injected iv in sheep, both separately and in combination. Plasma levels of immunoreactive ACTH (IR-ACTH), cortisol, and aldosterone were measured for 3 h after the injections. Mean levels before injections were 8 +/- 4 pmol/l for ACTH, 7 +/- 3 nmol/l for cortisol, and 28 +/- 9 pmol/l for aldosterone. CRF caused a rapid rise in IR-ACTH and a peak level of 125 +/- 52 pmol/l was obtained 15 min after injection. Highest values for cortisol and aldosterone levels were 40 +/- 9 nmol/l and 64 +/- 13 pmol/l, respectively, 30 min after injection. AVP also increased IR-ACTH (maximum level: 202 +/- 77 pmol/l at 5 min) and aldosterone (128 +/- 36 pmol/l at 15 min), whereas the cortisol increase was lower than after CRF. Simultaneous injection of CRF and AVP produced an addition of the IR-ACTH response (295 +/- 82 pmol/l at 15 min), but the changes in cortisol levels were similar to those obtained after CRF alone and those in aldosterone levels resembled those induced by AVP alone. Plasma Na and K, osmolality, and plasma renin activity (PRA) were not modified by either CRF or AVP. It is suggested that the increase in aldosterone levels after CRF could be mediated by ACTH and that after AVP by an IR-ACTH peptide with less effect on cortisol secretion.

Influence of psychosomatic stress in pregnant guinea-pigs on fetal lipid metabolism

After a psychosomatic stress applied to pregnant guinea-pigs, 7 or 1 day before term, plasma cortisol and non-esterified fatty acid levels increased immediately in mother and fetus. Plasma levels of cortisol and non-esterified fatty acids in newborns of mothers stressed 1 day before term were lower than in newborns of control mothers. The prenatal stress changed composition of triacylglycerol and phospholipids in newborn liver by inhibiting the postnatal increase of triacylglycerol and phospholipid stearic acid and by inhibiting the postnatal decrease in phospholipid palmitic, palmitoleic, linolenic and arachidonic acids.

Plasma ACTH, cortisol and aldosterone concentrations in chronically cannulated ovine fetuses and in lambs injected with ovine corticotropin releasing factor

Synthetic oCRF was intravenously injected into 3 groups of 5 chronically cannulated ovine fetuses in utero on days 120, 130 and 137 of gestation (10 micrograms/fetus). The respective twin fetuses were used as controls. Ovine CRF was also intravenously injected into 4 groups of 6 lambs on days 1, 3, 7 and 20 after birth (5 micrograms/kg bw). Fetal plasma ACTH and cortisol concentrations increased significantly following oCRF as early as 120 days of gestation without changing maternal plasma cortisol concentrations. The ACTH and cortisol response to CRF increased gradually on stages 130 and 137 of gestation, but on the other hand, plasma aldosterone did not change. In newborns, after oCRF, the pituitary response gave peak values at 10 min for plasma ACTH and adrenal response gave peak values at 15 min for plasma cortisol. Between 1 and 20 days, plasma ACTH and cortisol changes after oCRF decreased in older animals while aldosterone level remained unchanged. In animals receiving both treatments on days 1 and 20, plasma cortisol levels were increased for longer than in animals treated once.

The regulation of glucocorticosteroid secretion during the perinatal period

The regulation of adrenal activity during the perinatal period raises different experimental problems; studies are often limited and their conclusions vary with the species studied. During the perinatal period, the profile of the ratio of adrenal weight to body weight reaches a minimum earlier the more mature is the species; this minimum occurs before birth in sheep, at birth in guinea-pigs and 10 days after birth in mice. In mature species, fetal plasma cortisol is higher than that of the mother; it rises sharply near term. In other species, maternal plasma cortisol remains higher than that of the fetus which also rises during the days before birth. In all species, the fetal adrenal is activated concomitantly with a sharp increase of the action of corticosteroid binding globulin on fetal plasma. The origins of this protein in the fetal plasma and the regulation of its concentration are topics of actual research. Before birth, placental transfer of cortisol increases regularly and slowly. During the perinatal period it is demonstrated that fetal catabolism of cortisol augments up to the adult level independently of changes in hormone secretion around birth.

The development of cortisol metabolism in the perinatal period in the guinea-pig

Cortisol metabolism appears to be active soon after birth in guinea-pigs. Indeed, plasma cortisol half-life measured in three day-old animals resembles that of adult guinea-pigs (48 min). The metabolic clearance rate (MCR) of plasma cortisol as measured by continuous infusions of 3H-cortisol in fetal and newborn guinea-pigs remained very low, increasing slowly and regularly during the perinatal period without abrupt change at birth. Whole cortisol MCR in fetus is presented as the resultant of the concomitant actions of three factors: transfer to the mother, fetal irreversible removal rate and placental metabolism. True fetal cortisol MCR could be dissociated from total cortisol MCR measured in fetus by comparing the ratios of other measured parameters in maternal and fetal plasmas. Until ten days post partum, cortisol MCR varied independently of body weight growth and reflected the maturation of catabolizing hepatic enzymes.

The effects of psychosomatic stress at the end of pregnancy on maternal and fetal plasma cortisol levels and liver glycogen in guinea-pigs

Plasma cortisol and liver glycogen were measured in the mother, fetus and newborn of guinea-pig after a stress on days 60 and 67 of gestation (parturition occurring on day 68); at those times, the animals were held for 3 h in the dark and subjected to a flash of 75 J intensity every 10 sec. In comparison with the controls, stress increased plasma cortisol in both mothers and fetuses. While it decreased maternal liver glycogen on day 60, it increased fetal liver glycogen at the same stage. Glycemia decreased in mothers after stress, although at delivery females previously stressed on day 60 showed hyperglycemia.

Electrolyte balance, mode of delivery and plasma aldosterone levels in newborn lambs

Plasma aldosterone, sodium (Na) and potassium (K) concentrations, daily Na and K intakes, and urinary and faecal excretion were measured during the first week of postnatal life in 9 lambs naturally born at term (145 days of gestation) and in 10 lambs delivered by caesarean section on day 145 (6 lambs) or on day 139 (4 lambs) of gestation. Plasma aldosterone, Na and K concentrations showed no significant variation during the experimental period in any group of lambs, and there was no significant difference concerning these parameters among the three groups. Na and K balances were always positive during the experimental period in naturally born lambs. It was negative on days 4 and 6 postdelivery in those delivered by caesarean section on days 145 and 139 of gestation, respectively. This was probably due to the lower daily Na and K intakes measured in these 10 lambs compared to the 9 control lambs: urinary output and urinary Na and K excretion were lower in the two groups of lambs delivered by caesarean section, while Na and K urinary concentrations were not different in any group.

The conversion of cortisol into its principal metabolites, their tissular concentrations and transplacental transfer during 3H-cortisol infusion of mother and fetal guinea-pigs

During continuous infusion of 3H-cortisol in the circulation of the guinea-pig mother or fetus, radioactive metabolites appear in both maternal and fetal blood. These cortisol-derived compounds were identified principally as cortisone, tetrahydrocortisol (THF) and tetrahydrocortisone (THE). There were unidentified others in low quantities. The cortisone of the maternal plasma is 100% maternal in origin since that of the fetal plasma is 50% fetal in origin between days 62 and 66 and increased thereafter. An identical profile was noted for THF. THE seemed to be synthetized in the fetal guinea-pig and was transferred to the mother in increasing amounts near term. Liver concentrations of cortisol were higher than those of plasma in the mother. Maternal liver appeared to be the main organ of cortisol metabolism in the mother-fetus unit, but maternal adrenal may contribute to this metabolism.

Plasma calcium homeostasis in the guinea pig during the perinatal period

In pregnant guinea pigs on day 60 of gestation, maternal hypercalcemia induced by calcium infusion (10 mg Ca/kg body weight/h, during 2 h) had no significant effect on the fetal plasma calcium level. By contrast, on day 66 of gestation the same infusion of calcium into the pregnant female induced a significant rise both in maternal and fetal plasma calcium levels. This difference might be related to the variations in the efficiency of placental calcium transfer occurring during the last days of gestation in the guinea pig. Plasma calcium, phosphate and magnesium levels decrease during the 12 h following birth in suckling guinea pigs. Plasma calcium and magnesium concentrations returned to normal values at 24 h while plasma phosphate levels increased during the first week of postnatal life.

Role of testosterone in the sexual dimorphism of adrenal activity at puberty in the guinea-pig

Sexual dimorphism in adrenal activity appeared during the pubertal period of the guinea-pig with plasma levels and binding of cortisol lower in male guinea-pigs compared with female, and metabolic clearance rate (MCR) of cortisol higher in male than in female animals. Gonadectomy of female guinea-pigs did not change the values of the parameters regulating adrenal activity. Castration of male guinea-pigs caused a rise in plasma cortisol levels by increasing the binding capacity of transcortin for cortisol and by decreasing cortisol MCR. Treatment of females with testosterone from day 24 produced a drop on day 50 in plasma cortisol levels following a decreased binding capacity of transcortin for cortisol and at the same time as cortisol MCR increased. Furthermore, the adrenal response to stress was higher in castrated than in control males and lower in testosterone-treated females compared with control females. Testosterone appeared to be the hormone responsible for sexual dimorphism in adrenal activity in the pubertal guinea-pig.

Changes in cortisol binding and metabolism during neonatal development in the guinea-pig

The metabolic clearance rate and the binding of cortisol in plasma of male and female guinea-pigs were estimated at five stages between birth and weaning. The metabolic clearance rate for cortisol remained low in both sexes until day 10 post partum but increased to adult values by day 20. The level of free cortisol in plasma and the cortisol binding capacity of the plasma were higher at birth than on day 10 post partum; the values found on day 20 were similar to those of the adult guinea-pig. Surgical stress increased levels of cortisol in plasma on day 20 but not at birth.

Maturation of glucocorticosteroid activity in the foetal guinea-pig during the end of gestation

Cortisol levels were very high in maternal and foetal plasma during the last days of pregnancy. The percentage of free cortisol was maximal in plasmas of the mother and the foetus on the last day before parturition; the increase in free cortisol levels resulted from the saturation of transcortin binding capacity and from a higher adrenal secretion rate at that time due to stress at the onset of labor. On the last day of pregnancy the foetal adrenals could cover the hormonal needs of the foetus, the foetal-maternal transfer of cortisol being similar to the maternal-foetal transfer. However, the low TCM at cortisol indicated that cortisol catabolism was still immature. The origin of foetal transcortin is still unknown.

Foetal-maternal production and transfer of cortisol during the last days of gestation in the guinea-pig

The metabolism and the rate of transfer of cortisol across the placenta in pregnant guinea-pigs and foetuses were studied by constant intravenous infusions of tritium-labelled cortisol. Estimates of endogenous and radioactive plasma cortisol levels were used to calculate the following parameters at four stages before parturition (days 62, 64, 66 and 67; parturition occurring at day 68): metabolic clearance rate; production rate; adrenal secretory rate; transfer rate from mother to foetus and from foetus to mother; irreversible removal rate; the fraction of cortisol derived from the other in the foetal and maternal vascular compartments; the fraction of secreted and recycled cortisol involved in the transfer. The metabolic clearance rate and the rates of production and secretion of cortisol were higher in the mother than in the foetus between days 62 and 67 of gestation. About 90% of the foetal cortisol was of maternal origin. The fraction of maternal cortisol of foetal origin increased in the last days of gestation.

Perinatal changes in plasma and adrenal corticosterone and aldosterone concentrations in the mouse

The concentrations of corticosterone and aldosterone in the plasma and adrenal glands of foetal, newborn and mother mice were estimated during the last 4 days of pregnancy and throughout the perinatal period. The level of corticosterone in the maternal and foetal plasma fell from day 17 of gestation until birth, and then remained stable. Whereas the corticosterone content of the maternal adrenal glands did not change significantly, that of the foetal adrenal glands reached a peak on day 19 of gestation. At every stage of gestation, the level of corticosterone in the maternal plasma was higher than that in the foetus. Changes in the concentration of aldosterone in the foetal plasma and adrenal glands were similar and characterized by peak values at birth. In the mother during the last 4 days of pregnancy, the level of aldosterone in the plasma was higher than in non-pregnant mice, but lower than that in the foetus.

Plasma and adrenal cortisol concentrations in foetal, newborn and mother guinea-pigs during the perinatal period

Concentrations of cortisol, corticosterone and cortisone in the plasma and adrenal glands, liver glycogen and plasma glucose of foetal, newborn and mother guinea-pigs were estimated during the last 6 days of pregnancy and throughout the first 24 h post partum. At the same time progesterone was measured in the plasma of the mother. During the prepartum rise in foetal plasma cortisol levels and liver glycogen, no significant change in the foetal adrenal cortisol content was observed. The plasma and adrenal cortisol concentrations of the mother were much higher than those observed in the foetus and increased significantly before parturition. In the mother as in the foetus, cortisone and corticosterone represent only a small percentage of corticosteroids compared with cortisol. These results indicate that the autonomous capacity of foetal adrenals, inhibited by maternal secretions before term, appears suddenly at birth.

Changes in the concentrations of cortisol and corticosterone in the plasma and adrenal glands of the guinea-pig from birth to weaning

Concentrations of cortisol and corticosterone in the plasma and adrenal glands of male and female guinea-pigs were estimated throughout the first postnatal day and thereafter at intervals up to 3 weeks of age. In the guinea-pig, the basal level of cortisol secretion is established more slowly than in other species. The concentration of plasma cortisol is very high at birth, with a marked fall between days 1 and 10 post partum and then a steady level from day 10 to 20, the time of weaning. At day 10 the values for plasma cortisol and corticosterone approach the lower ones found in the adult. There were peaks in the amounts of corticosteroids found in the adrenal gland at 50 h, 4 and 7 days and these may have been due to increased hormonal synthesis between days 2 and 8.