Biomedical subjects

A Armario

Publications and source records attributed to A Armario.

At least 109 records · Page 6Linked to original sources

PubMed1986

Adrenocorticotropin administration increases testosterone secretion in adult male rats.

It appears that the effect of acute administration of pituitary-adrenal hormones on the pituitary-gonadal axis is species-dependent. However, no information is available with regard to the effect of acute adrenocorticotropin (ACTH) administration on testosterone secretion in rats. The present data indicate that acute ACTH administration can increase serum testosterone levels without modifying luteinizing hormone (LH) levels. Since this rise was not observed in castrated rats, it must be assumed that increased serum testosterone was of gonadal origin. The action of ACTH on testosterone secretion was likely an indirect one since there is no evidence at present for a direct, short-term action of the pituitary-adrenal axis on Leydig cell function.

Adrenocorticotropic Hormone↗

PubMed1986

Restraint stress induced changes in rat liver and serum metallothionein and in Zn metabolism.

24 h of a psychogenic stress (restraint) caused a strong increase of liver metallothionein (MT) levels. 3 h of stress were sufficient to induce an increase in liver MT, measured 21 h later, but the increase was much lower than in continuously restrained rats. Stress induction of liver MT was not due to food deprivation, since rats deprived for 24 h showed lower MT levels than stressed ones. Zn on MT presented the same qualitative but not quantitative pattern of response as MT protein. Liver cytosolic Zn was increased by restraint in spite of their being no decrease in serum Zn. Any treatment altered serum MT. Liver and serum MT were not correlated. The present results demonstrate that basically psychogenic stresses increased liver but not serum MT levels. No positive evidence for a relationship between corticosterone secretion and MT induction was found.

Animals↗

PubMed1986

The influence of restraint stress in rats on metallothionein production and corticosterone and glucagon secretion.

Earlier studies on metallothionein (MT) induction by stress used a wide range of stimuli, all of them considered as physical stressors. The present paper reports the effect of a basically psychogenic stress such as restraint on serum and liver MT. Male adult rats were stressed for 1, 12, 24 and 48 hours and then killed. Liver MT increased continuously throughout the experimental period. Rats deprived of water and food for 24 and 48 hours showed higher liver MT levels than control but lower levels than stressed ones. Serum MT was not modified by either restraint or water and food deprivation. The lack of relationship between the two MT pools was corroborated by the absence of a significant correlation between them. Restraint stress increased serum corticosterone but not glucagon levels, suggesting that only glucocorticoids are important in MT induction by stress. However, a strong circadian rhythmicity was observed in serum corticosterone but not in serum or liver MT in non-stressed rats. In addition, preliminary data with adrenalectomized rats indicate that glucocorticoids seem not to be essential in MT induction by stress. Likewise glucagon does not appears to be associated with MT induction by stress since its levels were not modified by restraint.

Adrenalectomy↗

PubMed1986

Sensitivity of anterior pituitary hormones to graded levels of psychological stress.

The effect of graded levels of stressor intensity on anterior pituitary hormones was studied in adult male rats. Corticosterone, considered as a reflection of ACTH release, and prolactin responses showed a good correlation with the intensity of the stressors. On the contrary, neither LH, GH nor TSH release showed a parallelism with the intensity of the stressors in spite of the fact that they clearly responded to all the stimuli. It appears that the hormones of the anterior pituitary might be divided into two groups: those whose response is sensitive to the levels of emotional arousal elicited by stress, and those displaying a clear but stereotyped response during stress. However, other alternative explanations might exist to justify the present results. The neural mechanisms underlying the two types of response are at present unknown. These data indicate that only the pituitary-adrenal axis and prolactin have some potential utilities as quantitative indices of emotional arousal elicited by currently applied stressors in the rat.

Animals↗

PubMed1986

Effects of water restriction on circadian rhythms of corticosterone, growth hormone and thyroid stimulating hormone in adult male rats.

The effects of acute and chronic water restriction on the circadian rhythms of corticosterone, growth hormone (GH), and thyroid stimulating hormone (TSH) were studied in adult male rats. Water restricted rats were allowed to drink between 9:00 and 9:30 a.m. only. Chronic water restriction but not one day of such treatment altered the circadian pattern of corticosterone so that a peak of this hormone appeared before water presentation. In contrast, neither acute nor chronic water restriction altered the qualitative patterns of circadian GH and TSH rhythms although both treatments depressed the secretion of the two hormones, the depression being greater in chronic than in acute water restricted rats. These results indicate that water restriction did not resynchronize the GH and TSH circadian rhythms. It appears that reduced secretion of GH and TSH observed in water restricted rats would be due to the concomitant reduction in food intake.

Animals↗

PubMed1986

Sensitivity of corticosterone and some metabolic variables to graded levels of low intensity stresses in adult male rats.

Adult male rats were subjected to different acute stressors, whose intensity was gradually increased, and their corticosterone, glucose, and serum lipid levels were studied. Serum corticosterone was sensitive to graded levels of stress intensities. Glucose followed the same trend. However, serum lipid responses were not related to the intensity of stress. Our results indicate that these latter variables were not sensitive indices of the emotional arousal elicited by brief stress stimuli.

Animals↗

PubMed1986

Response of anterior pituitary hormones to chronic stress. The specificity of adaptation.

The effect of chronic noise stress on the response of anterior pituitary hormones to the same or to another stressor (forced swimming) was studied in adult male Wistar rats. Both acute stressors increased corticosterone, prolactin, LH and TSH secretion and inhibited GH secretion. Previous chronic exposure to noise reduced corticosterone response to the same stimulus without modifying corticosterone response to a novel acute stress. Neither prolactin nor TSH responses to acute noise were reduced by previous chronic exposure to noise. Since chronic noise increased basal levels of LH and decreased those of GH, the response of these hormones to acute stress was expressed as percent changes of their respective basal values. It was found that chronically stressed rats showed diminished LH response to noise but not to forced swimming. GH showed the same pattern without reaching statistical significance. These data indicate that the response of some anterior pituitary hormones can adapt after repeated exposure to the same stressor. When adaptation occurred, this was specific for the stressor which the animals were repeatedly exposed to. The pituitary-adrenal axis appears to be the most reliable index of adaptation to chronic stress among all the anterior pituitary endocrine axes.

Acute Disease↗

PubMed1986

Pituitary gonadal function in adult male rats subjected to crowding.

The effect of crowding on the pituitary-gonadal axis was studied in adult male rats. Crowding reduced body weight gain, did not alter relative adrenal weight and increased relative testis weight. Neither basal levels of corticosterone nor its response to acute stress were altered by crowding. Likewise, LH secretion was similar in control and crowded rats. Prolactin levels tended to be lower in crowded than control rats, but they did not reach statistical significance. In contrast, impaired testosterone secretion was observed in crowded rats, at least in part due to reduced Leydig cell responsiveness to gonadotropin release. In addition, some mechanisms other than pituitary-adrenal hyperactivity might be responsible for reduced testosterone secretion during crowding.

Adrenal Glands↗

PubMed1986

Metabolic effects of chronic ACTH administration, interaction with response to stress.

The present experiment was undertaken to study the metabolic response to stress of single or chronic ACTH-treated male rats. It was found that chronic ACTH-treated rats showed a slight reduction in food intake and a decrease in body weight gain. This treatment increased basal serum triglyceride and insulin levels. In addition, some differences in response to stress was found in chronic ACTH-treated rats. Thus, these latter animals, unlike the other two groups, showed a decrease in circulating triglyceride and insulin levels in response to short-term stress. Moreover, 24 h after onset of stress a more marked fall in liver weight and glucose levels were found in chronic ACTH-treated rats. It suggests that chronic ACTH treatment might alter the metabolic response to prolonged acute stress what could result in lower resistance to severe stresses.

Adrenocorticotropic Hormone↗

PubMed1985

Dissociation between adrenocorticotropin and corticosterone responses to restraint after previous chronic exposure to stress.

The effect on emotional reactivity produced by a model for chronic stress in which different types of acute stresses were randomly combined for 29 days was studied in adult male rats. Chronically stressed rats showed a slight decrease in body weight gain and an increase in relative adrenal weight. Chronic stress did not modify defecation rate but reduced exploratory activity in the holeboard. Neither basal nor acute-stress induced levels of adrenocorticotropin (ACTH) were modified by previous chronic stress. Likewise, basal corticosterone levels were similar in both groups. However, corticosterone response to acute restraint stress was higher in chronically stressed than in control rats. The mechanisms underlying the dissociation between ACTH and corticosterone as well as its possible implications are discussed.

Adrenocorticotropic Hormone↗

PubMed1985

Post-weaning crowding induces corticoadrenal hyperreactivity in male mice.

The effect of various population densities on corticoadrenal function was studied in prepuberal male mice. High population densities decreased body weight gain. Neither adrenal weight nor basal serum corticosterone were modified by crowding. However, corticoadrenal response to some acute stresses such as noise and forced swimming was higher in crowded mice. As corticoadrenal response to adrenocorticotropin remained unaffected, it appears that crowding induced pituitary-adrenal hyperreactivity. Neither the defecation rate nor exploratory activity were altered by crowding, suggesting a dissociation between pituitary-adrenal responsiveness and behavioral measures presumably related to emotional arousal. These discrepancies may possibly be due to the higher sensitivity of corticoadrenal function to environmental changes. Our results suggest that crowding would be suitable as a model for chronic continuous stress.

Acute Disease↗

PubMed1985

Chronic noise stress and insulin secretion in male rats.

The effect of chronic noise, followed by acute noise and forced swimming, on basal glucose and insulin levels was studied in adult male rats. Chronic noise did not modify basal levels of either measured variable before or after the exposure of rats to acute stress. Acute noise decreased serum glucose and insulin levels, although hypoglycemia was transient. Forced swimming decreased insulin and increased glucose levels. Our results indicate that: serum insulin levels were sensitive to both physiological and psychological stresses, forced swimming caused more marked glucose and insulin responses than noise exposure, chronic intermittent noise did not alter pancreatic function, and no sign of adaptation was apparent after repeated exposure to noise.

Acute Disease↗

PubMed1984

Post-weaning differential housing and testosterone secretion in male mice.

The effect of different densities of animals per cage on basal testosterone secretion and its response to some stimuli was studied in prepuberal male mice. Mice housed with 110 or 55 cm2 of floor space per animal showed the same basal serum testosterone and hCG-induced testosterone release. Likewise, in a second experiment, the same basal serum testosterone and a similar response to acute noise stress were found in mice housed at 132, 66 or 22 cm2 of floor space per animal. These results suggest that post-weaning crowding did not affect Leydig cell function in male mice.

Adrenal Glands↗

PubMed1984

Effect of acute and chronic stress on testosterone secretion in male rats.

The effect of acute and chronic stress on serum testosterone was studied in adult male Wistar rats. Acute noise-light stress and the presence of a dog, but not change of room, raised serum testosterone. This testosterone was of gonadal origin since noise-light stress did not increase serum testosterone in castrated rats. Chronic noise-light did not modify either testes weight or serum testosterone. This suggests that chronic stress did not necessarily lead to impairment of endocrine function of the testes in the rat.

Animals↗

PubMed1984

Effect of crowding on some physiological and behavioral variables in adult male rats.

The effect of two population densities on body weight gain, food and water intake and the weight of some organs and glands was studied in adult male rats. Behavioral reactivity to open field was also assessed. Crowded rats (10 animals per cage) showed lower body weight gain than control rats (3 per cage) throughout all the experimental period. Crowding decreased food intake and increased water intake. Any effect of crowding on the weight of thymus, liver and endocrine glands (except testes) was found. Open field defecation and activity were the same in control and crowded rats. Discrepancies from earlier works could likely be due to methodological differences and these are discussed in the text.

Animals↗

PubMed1984

A comparison of corticoadrenal and gonadal responses to acute immobilization stress in rats and mice.

The effect of different periods of acute immobilization stress on circulating corticosterone and testosterone was studied in adult male rats and mice. Although initial corticoadrenal response to immobilization was similar in both species, this differed after a more prolonged exposure to the stress stimulus. This suggests that behavioral adaptation to long-lasting stimulation and/or effectiveness of corticosterone feedback on the hypothalamus-pituitary-adrenal axis could be different in those species. An inhibition of testosterone secretion after 5 hr of immobilization was observed in both rats and mice. However, mice seem to be more sensitive to stress-induced inhibition of testosterone secretion than rats. No evidence for a biphasic testosterone response to stress was found.

Adrenal Cortex↗

PubMed1984

Adaptation of anterior pituitary hormones to chronic noise stress in male rats.

We have studied the effects of acute and chronic noise on serum levels of pituitary hormones in male Wistar rats. Acute noise increased serum levels of corticosterone, prolactin, and luteinizing hormone and decreased serum GH. FSH was unaffected by this stressor. Chronic noise did not modify basal levels of any hormone studied, however responsiveness of some hormones to the same stimuli was altered. Reduced corticosterone, prolactin, and GH responses to noise was observed after previous chronic exposure to this stimuli. LH response followed the same pattern although it did not reach statistical significance. It might be concluded that adaptation to a repeated stress stimulus is not confined to the pituitary-adrenal axis, however, the degree of adaptation could vary between different hormones.

Animals↗

PubMed1984

Dissociation between corticosterone and growth hormone adaptation to chronic stress in the rat.

We have studied the effect of acute and chronic stress on corticosterone and growth hormone (GH) serum levels in male Wistar rats. Both acute noise-light stress and the presence of a dog elicited an increase in corticosterone and a decrease in GH levels in serum. While previous chronic stress induced a reduction of corticosterone response to the same stimuli, no reduction was observed in GH response. In addition, chronic exposure to noise-light stress induced modifications in corticosterone but not in GH response to dog presence. The results suggest that GH and corticoadrenal response mechanisms of adaptation to chronic stress are dissociated. This is further corroborated by the study of the correlation between both hormones.

Adaptation, Physiological↗