Hormonal and electrolyte response to exposure to 17,500 ft.

Hormone, electrolyte, and body fluid compartment changes were studied in subjects who either spent time at 10,000 ft before flying to 17,500 ft or were premedicated with acetazolamide and flown directly to 17,500 ft. In the former group, at 10,000 ft, renin and aldosterone were not different from control. Cortisol increased significantly from 9.8 to 19.5 mug/100 ml on the third day. At 17,500 ft, renin, aldosterone and cortisol were significantly elevated on day 3 but had returned to control levels by day 5. Sodium and potassium excretion was significantly reduced at both altitudes. Total body water, extracellular and plasma volume were reduced (P less than 0.05) at 17,500 ft. Subjects pretreated with acetazolamide and flown directly to 17,500 ft had significant increases (P less than 0.001) in plasma renin, aldosterone, and cortisol levels during the first 4 days at altitude. On day 1 there was a decrease of 45% in sodium and 38% in potassium excretion. On day 4 there was a decrease of 63% and 51%, respectively. These changes are not associated with the premedication. The initial changes may reflect the immediate response to stress and alkalosis followed by a return to control levels as the body adapts to altitude.     

Effect of metoclopramide-induced prolactin on aldosterone secretion in normal subjects

We investigated the role of prolactin (PRL) on modurating the secretion of aldosterone in normal male subjects. Metoclopramide (5mg) which causes a significant rise of PRL was given by intravenous injection. The peak of PRL level at 30 min. after i.v. injection of metoclopramide (20.0 ± 1.6 ng/ml, mean ± S.E.) was significantly higher than the basal level (6.4 ± 2.1 ng/ml, P < 0.01), but plasma aldosterone, serum sodium, potassium and plasma renin activity did not change significantly throughout the period of the study. Cortisol levels, however, reduced significantly after 30 min. and remained significantly low, probably because of diurnal variation. Present results suggest that PRL might at least not play a physiological role on regulating the secretion of aldosterone in man.     

Plasma aldosterone levels in two reptilian species,Uromastix acanthinurus andTiliqua rugosa, and the effect of several experimental treatments

Summary Plasma aldosterone concentrations have been measured by radioimmunoassay in two lizard species,Uromastix acanthinurus andTiliqua rugosa, and control levels were 36.04±4.73 ng/100 ml and 31.74±5.60 ng/100 ml respectively, which fall within the range reported for this hormone in mammals. Chronic salt loading for a period of 7 days depressed aldosterone levels in both species but chronic water loading produced a significant elevation only in the case ofUromastix acanthinurus. Plasma aldosterone and sodium concentrations were significantly correlated inUromastix (r=0.77) but the correlation was doubtful in the case ofTiliqua (r=0.41). Dexamethasone blockade for a period of 4 days depressed aldosterone levels inTiliqua rugosa but synthetic ACTH at a dosage of 2 I.U./100 g did not increase aldosterone concentrations in either species, although plasma corticosterone concentrations were elevated by the treatment. The extent to which aldosterone may be implicated in the regulation of sodium metabolism in reptiles and its possible action on extra-renal routes of electrolyte excretion is discussed.     

Effects of A and B prostaglandins on cAMP, cortisol, and aldosterone production by the human adrenal.

PGA₁ and PGA₂ (10, 100 μg/ml) significantly increased human adrenal cAMP levels and cortisol output but low doses (1 μg/ml) depressed both parameters. Only 1 μg/ml PGA₁ significantly increased aldosterone output while higher doses depressed same. The low PGA₂ dose (1 μg/ml) depressed aldosterone output. The glucocorticoid and mineralocorticoid outputs appear to be inversely modulated by prostaglandins. PGB₁ and PGB₂ behaved similarly to E type prostaglandins. However, like PGA₁, 1 μg/ml of PGB₁ or PGB₂ significantly increased aldosterone output. Higher doses were ineffective. The present findings reveal an increased complexity of prostaglandin modulation of cyclic nucleotides and steroid output.     

Serum steroid hormones in female Russian sturgeon (Acipenser gueldenstaedtii Br.) with normal oocyte maturation and with gonadal function disorders after hormonal stimulation

Blood serum cortisol, testosterone, and 11-ketotestosterone levels were determined by ELISA methods in female Russian sturgeon after hormonal stimulation for induction of ovulation. All females were divided into 5 groups depending on their initial reproductive status and response to hormonal stimulation; 1) normal ovulation, 2) ovulation followed by release of non-viable eggs, 3) normal state of ovary without ovulation, 4) lack of ovulation, early stage of oocyte resorption, 5) lack of ovulation, advanced stage of oocyte resorption. Cortisol levels in all five groups did not differed significantly. Testosterone levels were low (15-24 ng/ml) in females after ovulation and in females without response to hormonal stimulation because of early stage of oocyte resorption. Non-matured females with normal state of oocytes had significantly higher testosterone levels--82 +/- 16 ng/ml. Non-matured females with advanced stage of resorption were subdivided into 2 subgroups--with low (approximately 7 ng/ml) and high (> 100 ng/ml) levels of serum testosterone. 11-ketotestosterone levels were similar in all investigated groups of sturgeon.     

Study of plasma aldosterone in normal pregnancy, in pre-eclamptic women and in cord plasma of newborns.

A radioimmunoassay without chromatography was used for the determination of plasma aldosterone in pregnancy. The mean values (+/- S.D.) of aldosterone concentration increased consistently from 23.2 +/- 5.3 ng/100 ml (n = 14) during the first trimester to 37.2 +/- 10.6 ng/100 ml (n = 17) during the second trimester and 64.0 +/- 18.8 ng/100 ml (n = 29) during the third trimester of pregnancy. The highest values were found at delivery (71.9 +/- 14.2 ng/100 ml; n = 21) and in the cord plasma of newborns (83.4 +/- 14.9 ng/100 ml; n = 21). Significantly lower plasma aldosterone values were found in the plasma of pre-eclamptic women during the third trimester of pregnancy (41.9 +/- 21.3 ng/100 ml; n = 11).     

Plasma and uterine cortisol, progesterone and protein changes in pseudopregnant gilts treated with hydrocortisone acetate

To determine the effects of cortisol concentrations during pregnancy, gilts, made pseudopregnant through twice daily administration of 5 mg estradiol benzoate on Days 11 to 15 (Day 0 = first day of estrus), received either 5 mg/kg body weight of hydrocortisone acetate (HA) in sesame oil (n=5) or sesame oil alone (n=6) twice daily on Days 21 to 30. Blood samples (20 ml) were collected on Days 11, 21 and 31. Uterine flushings were obtained surgically on Day 31. The HA-treated gilts had higher (P<0.01) plasma cortisol (295.7 vs 35.6 ng/ml) and lower (P<0.01) plasma progesterone (8.9 vs 17.8 ng/ml) concentrations than did controls. Uterine flushings recovered from HA-treated gilts had significantly (P<0.01) higher cortisol (9.9 vs 5.6 ng/ml), lower progesterone (2.1 vs 6.8 ng/ml) and lower total protein (8.3 vs 21.4 mg/ml) levels than the control animals. Cortisol measured in the uterine flushings of the gilts was more than 85% unbound. Plasma corticosteroid binding globulin binding capacity was lower (P<0.05) in HA-treated gilts (7.4 nmol/l) than in the control (38.7 nmol/l) animals on Day 31. Corpora lutea (CL) number and weight were lower (P<0.05) in HA-treated than control gilts. However, progesterone concentration per CL did not differ between the 2 groups. These results indicate that elevated cortisol levels can alter endocrine and uterine functions related to pregnancy using the pseudopregnant gilt as a model.     

The reproductive cycle of Coregonus lavaretus (L) in Loch Lomond, Scotland, inrelation to seasonal changes in plasma cortisol concentration

The reproductive cycle of Coregonus lavaretus (L.) in Loch Lomond, Scotland, was investigated by monthly sampling. Spawing takes place during the first 3 weeks of January, on offshore gravel banks. Males congregate on the spawning-grounds throughout the spawning period, while ripe females cruise in unisexual shoals in deeper water. Individual females migrate to the spawning-grounds as ovulation takes place, spawn, and return to deep water. After spawning, the gonadosomatic ratio and somatic condition factor of both sexes decrease until June or July. Gonad recrudescence occurs in males between July and October, and in females between July and December. The somatic condition factor of both sexes rises from its minimum in June or July to its maximum in September. A competitive protein binding assay was used to determine cortisol levels in 0–1 ml plasma samples of individual fish. The lowest cortisol levels occurred in fish caught by seine-netting and killed immediately by anaesthesia in MS 222 (Sandoz). Seine-netting and killing by concussion induced higher cortisol levels, in the range of 3–5 ng/100 ml. Cortisol levels in fish caught by gill-netting for 18 h were 3–6 times higher than in seine-netted fish, and the method of killing was immaterial in this case. The length of time spent in the gill-net had no significant effect on cortisol level, but maintenance of the fish in aquaria for 24–80 h elicited high cortisol levels of over 50 μg/100 ml. Post-mortem delay before blood-sampling resulted in lowered cortisol levels. Seasonal variations in cortisol level were determined in gill-netted fish throughout the year, and in seine-netted fish when available. Cortisol levels were high in both sexes in September; and very high in ovulating females caught on the spawning-grounds, though not in ovulating females caught off the spawning-grounds.     

Influence of exposure to moderate altitude on the plasma concentraton of cortisol, aldosterone, renin, testosterone, and gonadotropins

The influence of 11 days at moderate altitude (2,000 m) combined with exercise on plasma concentration of testosterone, FSH (follicle-stimulating hormone), LH (luteinizing hormone), cortisol, aldosterone, and renin activity was studied in ten healthy subjects. Within 48 h of arrival at moderate altitude a significant increase in testosterone was found whereas FSH had decreased significantly and LH showed a tendency to decrease. Cortisol increased significantly at the beginning and reached a maximum at the end of altitude exposure. The plasma aldosterone level rose continuously and on the last day of altitude was significantly elevated. Plasma renin activity showed a tendency to decrease. On return to low land all measured parameters returned to base line values within 2 days. The findings of increases in plasma levels of aldosterone and testosterone (and serum T3 and T4, as reported by others) are in contrast to the previously found decrease of urinary excretion of all these hormones. This appears to be a distinct dissociation of serum levels of adrenal (and thyroid) hormones from their urinary excretion. The observed increase in plasma aldosterone is probably mediated through ACTH and the rise in plasma potassium, since plasma renin activity showed an opposite trend. The rise in plasma testosterone is probably of adrenal origin since plasma gonadotropins declined simultaneously. The increase of plasma levels of glucocorticoids, mineralocorticoids, and androgens after an ascent from 600 m to 2,000 m above sea level is compatible with an ACTH-mediated stimulation of the entire adrenal cortex and/or a diminished elimination of adrenal steroids: The concomitant fall of FSH, LH, and plasma renin would then be a consequence of a direct negative feedback inhibition of these hormones.     

Changes in the levels of growth hormones, insulin, cortisol, thyroxine and somatomedin-C/IGF-1, with increasing gestational age in the fetal pig, and the effect of thyroidectomy in utero

1. Blood samples were taken from 30 chronically catheterized pig fetuses in utero. Levels of growth hormone, insulin, cortisol, thyroxine and somatomedin-C/IGF-1 were measured in the plasma of intact fetuses and the plasma of thyroidectomized fetuses at various gestational ages during the latter part of pregnancy. 2. Growth hormone levels were high (mean +/- SEM: 83 +/- 9 ng/ml and remained constant throughout this period. 3. Insulin levels were also constant and ranged between 4 and 14 mU/l. 4. Cortisol levels showed a general increase from 400 nmol/l at 97 days to 1200 nmol/l at term and this increase was not affected by thyroidectomy. 5. IGF-1 levels were lower than in the sows (48.0 +/- 3.0 ng/ml) and did not change throughout this period. 6. Thyroxine levels were also unchanged at about 92 +/- 4 nmol/l. 7. Thyroidectomy resulted in lower (P less than 0.001) thyroxine levels (28 +/- 3 nmol/l) but had no effect on the levels of any other hormone.     

Basal plasma aldosterone levels and tetracosactid-induced increase of aldosterone secretion in conscious male rabbits: lack of correlation with glucocorticosteroid levels

The adrenocortical secretory activity under basal conditions and after treatment with tetracosactid (1-24ACTH) has been investigated in chronically cannulated male rabbits. Basal plasma concentrations of glucocorticosteroids (0.74 micrograms/100 ml) and aldosterone (78 pg/ml) have been determined in a greater number of animals. No significant positive correlation between basal glucocorticosteroid and aldosterone plasma levels could be found. After intravenous injection of 2.5, 5.0, 10.0 and 20.0 micrograms/kg body weight tetracosactid glucocorticosteroid concentrations were significantly elevated between 40--100 min after administration; aldosterone release, on the other hand, was significantly increased only after injection of 10.0 or 20.0 micrograms/kg body weight tetracosactid between 20--60 min after injection. After administration of high tetracosactid doses glucocorticosteroid and aldosterone plasma concentrations were significantly correlated (10.0 micrograms/kg: r = 0.62; 20.0 micrograms/kg: r = 0.26). Because of the relative insensitivity of the zona glomerulosa cells to tetracosactid administered intravenously, it is concluded that ACTH is only of minor importance in the regulation of aldosterone secretion in the rabbit.     

The Effect of Transport Stress on Plasma Levels of Catecholamines,Cortisol, Corticosteroid-Binding Globulin,Blood Cell Count,and Lymphocyte Proliferation in Pigs

The effect of transport stress on the plasma levels of catecholamines, Cortisol, and corticosteroid-binding globulin were studied in 6 gilts. To assess the effect on immune status, white blood cells were also counted and the cell-mediated immunity was estimated. The adrenaline level increased significantly during transport, from a basal mean level of 0.03 ng/ml to a plateau level of 0.11 to 0.12 ng/ml. The noradrenaline level fluctuated, but not constantly, during transport. The mean plasma Cortisol level before loading was approximately 40 nmol/1 and rose immediately after the start of transport to 70 nmol/1 (p< 0.05) and to 87 nmol/1 (p< 0.01) within 10 and 30 min, respectively. After unloading the Cortisol level rapidly decreased and a minimum level was seen 4 h after the transport, whereafter the diurnal rhythm was resumed. The plasma corticosteroid-binding globulin level increased nonsignificantly during the day of transport, from 25 nmol/1 to a level of 34 nmol/1, and it continued to increase until a plateau level was reached on the second day after transportation. The total white blood cell number increased significantly (from 13.7 to 15.5 × 109 cells/1), the number of lymphocytes decreased significantly (from 8.4 to 7.0 × 109 cells/1), and the number of polymorphonuclear neutrophils increased significantly (from 4.3 to 7.2 × 109 cells/1) during transport. No significant variation in the proliferation response was seen in the whole blood cell cultures. The main results were the significant signs of simultaneous activity of both the adrenal cortex and the adrenal medulla during transport.     

Action of Cortisol on Sodium Transport in Canine Erythrocytes

Incubation of blood from deoxycorticosterone-treated, adrenalectomized dogs with glucose, ²²NaCl, and cortisol, added in vitro, revealed log dose-related acceleration of sodium influx, of glucose utilization, and of lactate formation by cortisol in concentrations between 150 and 1000 µg/liter. Addition of 2-deoxyglucose, or preincubation of the blood until blood glucose concentration had fallen below 2.0 mg per 100 ml, reduced or abolished the acceleratory action of added cortisol on sodium influx but had no effect on sodium influx in the absence of added cortisol. Cortisol did not change the ATP or ATPase content of erythrocytes, or the metabolism of glucose via the pentose phosphate pathway, or the rate of efflux of ²²Na from the erythrocytes. The acceleratory actions of cortisol on sodium, influx, glucose utilization, and lactate formation were significantly correlated. Cortisol (1000 µg/liter) enhanced sodium influx by approximately 8.7 mmole per liter erythrocytes per hour for each 1 mmole cortisol-induced increment in ATP production. It is concluded that sodium influx in canine erythrocytes comprises a passive component, unchanged by cellular metabolism, and a second component which is accelerated and inhibited in proportion to prevailing plasma concentrations of cortisol and aldosterone, and which (for cortisol) depends upon accelerated ATP production via glycolysis. These steroid actions probably result from effects on enzyme activity rather than on new enzyme induction.     

Plasma Testosterone and Testosterone Binding Affinities in Men with Impotence,Oligospermia, Azoospermia,and Hypogonadism

Mean plasma testosterone levels (± S.D.), using Sephadex LH-20 and competitive protein binding, were 629 ± 160 ng/100 ml for a group of 27 normal adult men, 650 ± 205 ng/100 ml for 27 impotent men with normal secondary sex characteristics, 644 ± 178 ng/100 ml for 20 men with oligospermia, and 563 ± 125 ng/100 ml for 16 azoospermic men. None of these values differ significantly. For 21 men with clinical evidence of hypogonadism the mean plasma testosterone (± S.D.), at 177 ± 122 ng/100 ml, differed significantly (P < 0·001) from that of the normal men.The mean testosterone binding affinities (as measured by the reciprocal of the quantity of plasma needed to bind 50% of ³H-testosterone tracer) were similar for normal, impotent, and oligospermic men. Though lower for azoospermic men the difference was not significant (P >0·1). For 12 of the 16 hypogonadal males the testosterone binding affinity was normal, but raised binding affinities, similar to those found in normal adult females or prepubertal boys (about twice normal adult male levels), were found in four cases of delayed puberty. These findings help to explain why androgen therapy is usually useless in the treatment of impotence.     

Plasma Cortisol in the Horse,Diurnal Rhythm and Effects of Exogenous Acth

Peripheral blood plasma Cortisol concentration and its diurnal variation was measured in 4 horses. Mean concentration of Cortisol during 24 hrs. was 42 ng/ml (s ± 20 ng/ml). Peak values occurred at 6 a.m. and the lowest values were observed at about 6 p.m. (mean 65 ng/ml and 20 ng/ml, respectively). Long-acting ACTH at a dose of 150 i.u. was given by intramuscular injection to the 4 horses. Peak Cortisol concentrations markedly exceeding the prestimulation level were obtained between 2 and 4 hrs. after injection. During the immediate 24 hrs. after these peaks, the mean Cortisol level was markedly lower and the cyclic variation out of phase with the basal diurnal pattern. After a gradual adjustment during the second postinjection day, no differences could be seen between the 2 patterns on day 3 after injection.     

Suppression of plasma thyroid hormone concentrations by cortisol in the European eel Anguilla anguilla

Female European eels, Anguilla anguilla, were given a single intra-arterial injection via a catheter of cortisol hemisuccinate at doses ranging from 3.5 to 35 micrograms (15 to 150 micrograms/kg body wt), yielding mean plasma cortisol levels of 87-410 ng/ml 2 hr after injection. Cortisol treatment (17.5 and 35 micrograms) significantly decreased plasma levels of thyroxine (T4) and triiodothyronine (T3) within 24 hr relative to those in control fish. Cortisol treatment (35 micrograms) appeared to increase the clearance rate of 125I-T3 from plasma and the proportionate uptake of radioactivity in certain tissues after injection of 125I-T3. Cortisol treatment had no apparent effect on the plasma clearance of 125I-T4 or tissue distribution of radioactivity after injection of 125I-T4.     

Effects of acute stress, (1-24)ACTH administration and changes in superfusion temperature and flow rate on the in vitro secretion of glucocorticosteroids and aldosterone from the Mongolian gerbil (Meriones unguiculatus) adrenal gland

The release of glucocorticosteroids and aldosterone rapidly decreased after start of superfusion and reached a steady base-line within 60-90 min of superfusion. While secretion markedly varied between experiments, it was very constant in the same experiment (coefficient of variation: 7.4-2.2% for glucocorticosteroids and 5.8-3.9% for aldosterone). After repeated exposure of adrenal tissue to 1 IU/ml (1-24)ACTH, glucocorticosteroid release progressively increased; under the same conditions aldosterone secretion was not changed. Glucocorticosteroid secretion from glands of animals stressed by 1-hr confinement or of animals injected with 6 IU (1-24)ACTH was significantly higher than that of controls over the 60-min superfusion period. Aldosterone secretion was not affected significantly by these pretreatments. After reduction of temperature from 35 to 1 degrees C, steroid release ceased. Elevation of temperature from 12 to 32 degrees C resulted in a linear increase of glucocorticosteroid and aldosterone secretion. A highly significant positive correlation was found between glucocorticosteroid and aldosterone amounts secreted from adrenals superfused at temperatures between 1 and 35 degrees C (r = 0.91, n = 116, P less than 0.0001). Changes of flow rate from 0.5 to 1.5 ml/min for 5 min induced a short term (1 min) stimulation of glucocorticosteroid and aldosterone release; reduction of flow rate to 0.5 ml/min for 5 min drastically diminished secretion of steroids below control levels for 1 min.     

Endocrine Effects of Heat Stress in Boars

The purpose of this study was to describe the temporal changes in peripheral plasma levels of testosterone and Cortisol in boars during and after heat stress. A total of 8 boars were utilized, 4 of them were exposed to 35°C, for 100 h in a climatic room, and 4 served as controls and were kept at 20 °C for 100 h in the climatic room. Blood samples were obtained via permanent vein catheters 3 times daily from 5 days before heat stress until 20 days after termination of heat stress. Testestorone levels were determined by radioimmunoassay and Cortisol by a competitive protein binding technique. For both hormones the pre-exposure levels were similar in both groups of boars. The control boars had significantly higher testosterone levels, while being in the climatic room, than during any other period. The experimental boars had slightly increased testosterone levels during the first day of heat stress and thereafter continuously decreased levels. In the control boars the testosterone levels returned to pre-exposure levels immediately after removal from the climatic room, whereas in the experimental boars the testosterone levels were dramatically increased during the first 5 days after exposure. The differences in Cortisol levels, between the 2 groups of boars were restricted to the period spent in the climatic room. During this period the experimental boars had significantly higher Cortisol levels.     

Circadian rhythm of aldosterone in dairy cattle during the summer

Twelve Holstein heifers, pregnant from 120–150 days were used to study the circadian rhythm of aldosterone, cortisol, progesterone, sodium and potassium in dairy cattle during the summer in Louisiana. Cortisol was not significantly influenced by time (time 1 = 06.00 h). Aldosterone, sodium, potassium and progesterone changed significantly (P<.01) with time. Aldosterone peaked (116.5±17.2 pg/ml) at 08.00 h and then generally declined to 16.00 h (26.7±2.0 pg/ml). Sodium generally increased from 06.00 h (320.1±7.3 mg%) to 18.00 h (377.9±6.1 mg%), and then declined. Potassium generally increased from 06.00 h (20.9±0.5 mg%) to 22.00 h (23.0±0.3 mg%). Progesterone generally increased from 07.00 h (2.8±0.4 mg/ml) to 24.00 h (7.5±1.4 mg/ml). Aldosterone was significantly related to temperature associated with the time of the day samples were taken (r = 0.66, P<.02).     

Plasma aldosterone, renin activity, and cortisol responses to heat exposure in sodium depleted and repeleted subjects.

The effect of 90-min heat exposure (46 degrees C, 35 mbar) on plasma aldosterone (PA) patterns was studied and the respective roles of plasma renin activity (PRA), adrenocorticotropin (ACTH), Na+ and K+ concentrations in the control of PA response were in investigated in eight subjects on a low sodium diet and in five subjects on a high sodium diet. In all subjects, transitory PA increases of varying importance were observed, which were not related to sweat losses (less than 1% bodyweight) or to rectal temperature rise. In sodium-repleted subjects, basal PA and PRA levels as well as heat-induced rises were low (mean PA peak level = 12.62 +/- 1.15 ng/100 ml). They were enhanced by sodium depletion and PA reached a mean peak level of 34.07 +/- 2.73 ng/100 ml. But, in both conditions, the heat-induced PA peaks were 3-times higher than the initial levels. PA correlated with PRA in all but one of the sodium-repleted subjects and in 6 of the 8 sodium-depleted subjects. ACTH release, as measured by plasma cortisol (PC) levels, occurred in those subjects who noted an increased feeling of annoyance and discomfort. Thus, PA correlated positively with PC in 4 sodium-depleted subjects. A high sodium intake improved heat-tolerance. Plasma K+ and Na+ concentrations were not significantly modified by exposure to heat. PA increases can occur without concomitant changes in PRA, PC, K+ or Na+, which suggests that an additional factor may play a role in aldosterone regulation during acute heat exposure.