Age-related differences in basal and calcium-stimulated plasma calcitonin levels in female rats

1992 ◽  
Vol 262 (5) ◽  
pp. E557-E560
Author(s):  
C. L. Tsai ◽  
H. F. Pu ◽  
C. P. Lau ◽  
P. S. Wang ◽  
T. K. Liu
Keyword(s):  
Ovarian Function ◽  
Estradiol Benzoate ◽  
Young Female ◽  
Female Rats ◽  
Target Tissue ◽  
Young Rats ◽  
Ovx Rats ◽  
Age Related ◽  
Old Rats ◽  
Effects Of Aging

The effects of aging on calcitonin (CT) secretion in female rats were investigated. Old (24 mo) at constant diestrus status and young (2 mo) at diestrus status rats were either ovariectomized (Ovx) or left intact as controls. Ovx rats were injected subcutaneously with estradiol benzoate (25 micrograms/kg body wt) or sesame oil one time per day for 3 days. All rats were infused with CaCl2 (10 mg/ml) at a rate of 2 ml/h for 30 min via a jugular catheter connected to a peristaltic pump. Blood samples (0.5 ml each) were collected at 0, 30, 60, and 120 min. The basal and post-CaCl2 levels of plasma Ca measured with radioimmunoassay were significantly higher (P less than 0.05-0.01) in old than in young female rats. The pre- and post-CaCl2 levels of plasma Ca and CT in young rats were not altered by Ovx or estradiol replacement. In old rats, Ovx caused a higher (P less than 0.01) level in plasma CT at 0 and 30 min after CaCl2 infusion. Both basal and stimulated levels of plasma CT were higher (P less than 0.01) in old Ovx than in young Ovx rats. These results demonstrated that 1) the increase of plasma CT in response to Ca challenge was greater in old than in young female rats, 2) the influence of estradiol and ovarian function on plasma CT concentration increases as a function of age, and 3) estradiol reduced the plasma CT in response to hypercalcemia in old Ovx rats. The sensitivity of the target tissue of young rats may be lower in response to the modulation of estrogen during hypercalcemia without compromising the secretion and hypocalcemic effect of CT in young rats. All suggested an age-related relationship between estrogen and CT secretion in minute-to-minute regulation during Ca infusion in rats.

EFFECTS OF AGE AND OVARIAN FUNCTION ON THE PITUITARY–THYROID SYSTEM IN FEMALE RATS

1978 ◽  
Vol 78 (2) ◽  
pp. 225-232 ◽  
Author(s):  
H. J. CHEN ◽  
P. G. WALFISH
Keyword(s):  
Ovarian Function ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Lower Percentage ◽  
Female Rat ◽  
Thyrotrophin Releasing Hormone ◽  
Young Rats ◽  
Trh Stimulation ◽  
Old Rats ◽  
Absolute Concentrations

SUMMARY The effects of ovariectomy and ovariectomy and treatment with oestradiol benzoate (OB) on the basal concentration of thyrotrophin (TSH), the total concentrations and concentrations of free tri-iodothyronine (T3) and thyroxine (T4), and the concentrations of TSH, T3 and T4 observed after treatment with thyrotrophin releasing hormone (TRH) were studied in old (16–17 months of age) constant oestrous and young (3–4 months of age) oestrous rats. The untreated old control rats had significantly (P< 0·001) lower basal total T4 concentrations and percentage and absolute concentrations of free T4 and lower percentage and absolute concentrations of free T3 than untreated young rats. The basal levels of TSH in these two groups were similar and the increases in TSH after injection of TRH were identical. Two weeks after ovariectomy, no significant additional differences in hormone concentrations between old and young rats were observed. However, release of TSH induced by TRH was increased by three- to fourfold in old rats after ovariectomy compared with nine- to tenfold in young ovariectomized rats (P<0·01). Basal T4 concentrations remained unchanged in old ovariectomized rats treated for 7 days with 2 μg OB/day compared with both intact and ovariectomized rats. However, T4 concentrations in OB-treated young rats were significantly (P<0·001) reduced. Treatment with OB significantly increased both basal and TRH-induced T3 and TSH levels in old and young rats although the young rats showed a greater response (P<0·001). Two hours after injection of TRH, serum T3 concentrations in old rats increased only after OB treatment and not after ovariectomy alone or in intact rats, whereas T3 concentrations rose in all three groups of young animals. These results indicate that (1) older female rats have lower total T4, free T4 and free T3 concentrations and a lower TSH response to TRH, (2) OB treatment in young rats suppresses serum T4 but increases serum T3 and results in a greater TSH response to TRH and (3) at least one of the mechanisms accounting for the alterations in thyroid function observed in the older female rat, in addition to possible concomitant primary thyroid gland hypofunction, is a hyporesponsiveness of pituitary thyrotrophs to both endogenous negative feedback signals from low serum thyroid hormone concentrations and exogenous TRH stimulation.

Age-related alterations in prolactin binding sites in the female rat

1991 ◽  
Vol 124 (3) ◽  
pp. 314-321 ◽  
Author(s):  
Philippe Schneiter ◽  
Marianne J. Reymond ◽  
Thérèse Lemarchand-Béraud
Keyword(s):  
Binding Sites ◽  
Mammary Glands ◽  
Female Rats ◽  
Affinity Constant ◽  
Female Rat ◽  
Binding Studies ◽  
Young Rats ◽  
Age Related ◽  
Old Rats ◽  
Nulliparous Female

Abstract. Aging is associated with various neuroendocrine alterations, including in the rat a hypersecretion of PRL with maintained ovulations (repetitive pseudopregnancy) and a reduced activity of the hypothalamic dopaminergic neurons with loss of the neuron responsiveness to PRL, suggestive of age-related alterations in PRL receptors. In this study we have investigated PRL binding sites in the hypothalamus as well as in the mammary glands, the ovaries and the liver of young and old nulliparous female rats. The old rats (26-28 months) displayed spontaneous repetitive pseudopregnancies and they were compared with young (4-6 months) pseudopregnant rats; the binding studies were performed by saturation analysis using 125I-oPRL as ligand and particulate membrane preparations. In the hypothalamus, a negligible binding of PRL was observed in all fragments studied, mediobasal hypothalamus, median eminence, in both young and old rats and no characterization of the binding sites could be achieved. In the mammary glands, the number of PRL binding sites was appreciable in spite of the nulliparity of the rats, but it was smaller in the old than in the young rats (9.0±1.4 vs 14.9±1.2 fmol/mg protein; mean ± sem; p<0.02). In the ovaries, the density of PRL binding sites was similar in the old and young rats (112.6±9.7 vs 115.0±8.9 fmol/mg protein), illustrative of a maintained luteotropic effect of PRL with age in the rat. In contrast, in the liver a greater number of binding sites was found in the old than in the young rats (261.9±36.6 vs 63.6±5.8 fmol/mg protein; p<0.001), supportive of the ability of PRL to induce its own receptors in that tissue. The affinity constant of PRL binding was not altered with age in the tissues studied. These results are illustrative of tissue-specific modifications in the number of PRL binding sites with age and they are suggestive of a sustained biological activity of PRL in the old rats.

EFFECTS OF CASTRATION AND GONADAL STEROIDS ON SERUM LUTEINIZING HORMONE AND PROLACTIN IN OLD AND YOUNG RATS

1975 ◽  
Vol 66 (1) ◽  
pp. 45-51 ◽  
Author(s):  
C. J. SHAAR ◽  
J. S. EUKER ◽  
G. D. RIEGLE ◽  
J. MEITES
Keyword(s):  
Recovery Period ◽  
Young Female ◽  
Female Rats ◽  
Male Rats ◽  
Serum Prolactin ◽  
Absolute Increase ◽  
Young Rats ◽  
Serum Lh ◽  
Oestradiol Benzoate ◽  
Old Rats

SUMMARY Changes in serum LH and prolactin concentrations in response to bilateral gonadectomy and gonadal steroid replacement were measured in mature young (4–6 months) and old (23–30 months) female and male Long–Evans rats. On day 13 after gonadectomy, female rats were injected with oestradiol benzoate (OB) and male rats with testosterone propionate (TP) for a period of 12 days. They were then permitted a recovery period of 6 weeks. Serum prolactin and LH concentrations were measured by radioimmunoassay in single blood samples taken at various intervals before and after gonadectomy and during and after steroid treatment. Serum LH levels were about the same in intact young and old female rats, but after ovariectomy LH rose several fold higher in young than in old female rats. In male rats, serum LH values were about four times greater in intact young than in intact old rats, and after orchidectomy the increase in serum LH was greater in young than in old rats. Oestradiol benzoate and TP injections into female and male young and old rats produced variable effects on LH release. Serum prolactin concentrations were approximately six times higher in old intact than in young intact female rats, and after ovariectomy showed a much greater percentage reduction in old than in young female rats. Administration of OB produced a greater absolute increase in serum prolactin in old than in young female rats. Serum prolactin values were about the same in old and young male rats, and the effects of castration and TP administration on serum prolactin were not markedly different in the two age groups. These results indicate that old female and male rats are less capable of releasing LH than young rats of both sexes, but old females release more prolactin than young females.

Effects of trenbolone acetate and testosterone on growth and on plasma concentrations of corticosterone and ACTH in rats

1990 ◽  
Vol 126 (3) ◽  
pp. 461-466 ◽  
Author(s):  
M. N. Sillence ◽  
R. G. Rodway
Keyword(s):  
Weight Gain ◽  
Growth Response ◽  
Plasma Concentrations ◽  
Female Rats ◽  
Male Rats ◽  
Adrenal Weight ◽  
Trenbolone Acetate ◽  
Male And Female Rats ◽  
Age Related ◽  
Old Rats

ABSTRACT The effects of trenbolone acetate (TBA) on growth and on plasma concentrations of corticosterone were examined in male and female rats. At 5 weeks of age, rats were injected with TBA (0·8 mg/kg) dissolved in peanut oil, or with oil alone, daily for 10 days. In female rats, TBA caused an increase in weight gain (20–38%), a reduction in adrenal weight (19%) and a reduction in plasma concentrations of corticosterone (55%). In contrast, TBA-treated male rats showed no significant increase in weight gain, no significant change in adrenal weight and no reduction in plasma concentrations of corticosterone. The mechanism by which adrenal activity was suppressed in TBA-treated female rats was examined and the response compared with that to testosterone. Female rats (8 weeks old) were injected daily either with oil vehicle, TBA (0·8 mg/kg) or testosterone propionate (0·8 mg/kg). Testosterone increased weight gain (24%), but the growth response to TBA treatment was significantly greater (97%). A reduction in plasma concentrations of corticosterone (45%) was again observed in response to TBA. However, testosterone increased plasma concentrations of corticosterone (52%) above those of control values. Neither androgen affected plasma concentrations of ACTH. Finally, the effects of TBA were examined in 6-week-old female rats, to characterize further the apparent age-related increase in responsiveness. The growth response of 6-week-old rats (60–74%) was intermediate between that seen in 5- and 8-week-old animals. It is concluded that part of the anabolic activity of TBA may be related to a reduction in circulating concentrations of corticosterone. The effect of TBA on corticosterone concentrations differs from that of the natural androgen, testosterone, and does not appear to be mediated by a reduction in plasma concentrations of ACTH. Journal of Endocrinology (1990) 126, 461–466

scholarly journals Are skeletally mature female rats a suitable model to study osteoporosis?

2012 ◽  
Vol 56 (4) ◽  
pp. 259-264 ◽  
Author(s):  
Claudia Cardoso Netto ◽  
Vivian Cristine Correia Vieira ◽  
Lizanka Paola Figueiredo Marinheiro ◽  
Sherry Agellon ◽  
Hope Weiler ◽  
...  
Keyword(s):  
Bone Metabolism ◽  
Type I Collagen ◽  
Biomechanical Properties ◽  
Mature Female ◽  
Female Rats ◽  
Suitable Model ◽  
Type I ◽  
Age Related ◽  
Female Wistar Rats ◽  
Old Rats

OBJECTIVE: To analyze if female Wistar rats at 56 weeks of age are a suitable model to study osteoporosis. MATERIALS AND METHODS: Female rats with 6 and 36 weeks of age (n = 8 per group) were kept over a 20-week period and fed a diet for mature rodents complete in terms of Ca, phosphorous, and vitamin D. Excised femurs were measured for bone mass using dual-energy x-ray absorptiometry, morphometry, and biomechanical properties. The following serum mar-kers of bone metabolism were analyzed: parathyroid hormone (PTH), osteocalcin (OC), osteoprotegerin (OPG), receptor activator of nuclear factor Κappa B ligand (RANKL), C-terminal peptides of type I collagen (CTX-I), total calcium, and alkaline phosphatase (ALP) activity. RESULTS: Rats at 56 weeks of age showed important bone metabolism differences when compared with the younger group, such as, highest diaphysis energy to failure, lowest levels of OC, CTX-I, and ALP, and elevated PTH, even with adequate dietary Ca. CONCLUSION: Rats at 26-week-old rats may be too young to study age-related bone loss, whereas the 56-week-old rats may be good models to represent the early stages of age-related changes in bone metabolism.

Cardiac response to doxorubicin and dexrazoxane in intact and ovariectomized young female rats at rest and after swim training

2012 ◽  
Vol 302 (10) ◽  
pp. H2048-H2057 ◽  
Author(s):  
Annie Calvé ◽  
Rami Haddad ◽  
Sarah-Neiel Barama ◽  
Melissa Meilleur ◽  
Igal A. Sebag ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Adult Survivors ◽  
Young Female ◽  
Cardiac Response ◽  
Female Rats ◽  
Cancer Therapies ◽  
Sprague Dawley ◽  
Cardiac Damage ◽  
Ovx Rats ◽  
The Impact

The impact of cancer therapies on adult cardiac function is becoming a concern as more children survive their initial cancer. Cardiovascular disease is now a significant problem to adult survivors of childhood cancer. Specifically, doxorubicin (DOX) may be particularly harmful in young girls. The objective of this study was to characterize DOX damage and determine the ability of dexrazoxane (DEX) to reduce DOX-mediated cardiac damage in sedentary and swim-trained female rats. Female Sprague-Dawley rats were left intact or ovariectomized (OVX) at weaning then injected with DEX (60 mg/kg) before DOX (3 mg/kg), DOX alone, or PBS. Rats were separated into sedentary and swim cohorts. Body weight was reduced in DOX:DEX- but not PBS- or DOX-treated rats. Echocardiographic parameters were similar in sedentary rats. Swim training revealed greater concentric remodeling in DOX-treated rats and reduced fractional shortening in DOX:DEX-treated rats. Calsequestrin 2 was reduced with DOX and increased with DOX:DEX postswim. Sarco(endo)plasmic reticulum Ca2+-ATPase 2a was reduced and calsequestrin 2 reduced further by swim training only in intact rats. OVX rats were heavier and developed eccentric remodeling post-swim with DOX and eccentric hypertrophy with DOX:DEX. Changes in SERCA2a and calsequestrin 2 expression were not observed. Ovariectomized DOX- and DOX:DEX-treated rats stopped growing during swim training. DEX coinjection did not relieve DOX-mediated cardiotoxicity in intact or hormone-deficient rats. DOX-mediated reductions in growth, cardiac function, and expression of calcium homeostasis proteins were exacerbated by swim. DEX coadministration did not substantially relieve DOX-mediated cardiotoxicity in young female rats. Ovarian hormones reduce DOX-induced cardiotoxicity.

Effects of chronic estrogen treatment on water exchange in rats

1984 ◽  
Vol 247 (1) ◽  
pp. E101-E110 ◽  
Author(s):  
K. A. Carlberg ◽  
M. J. Fregly ◽  
M. Fahey
Keyword(s):  
Water Exchange ◽  
Daily Intake ◽  
Estradiol Benzoate ◽  
Female Rats ◽  
Intact Female ◽  
Water Turnover ◽  
Ovx Rats ◽  
Concentrate Urine ◽  
Daily Water ◽  
Intake Ratio

Intact female rats implanted subcutaneously with Silastic tubes containing estradiol benzoate (EB) (28.7 micrograms X kg-1 X day-1) for 28 wk had a significantly greater daily intake of water, a higher water-to-food intake ratio, and a greater urine output than untreated control rats. Ovariectomized (OVX) rats also implanted for 14 wk with EB tubes (15 and 36 micrograms X kg-1 X day-1) showed identical results. Dipsogenic responses of the EB-treated rats to isoproterenol (25 micrograms/kg sc), angiotensin II (200 micrograms/kg ip), and hypertonic saline (1 M, 1% of body wt ip) were significantly attenuated. Both intact and OVX rats were subjected to a 24-h dehydration to assess renal concentrating ability. EB-treated rats lost significantly more weight and excreted significantly more urine of lower osmolality than controls. Administration of vasopressin to volume-loaded, EB-treated rats revealed no abnormalities in the ability to concentrate urine to the level of controls. Thus, in spite of a reduced responsiveness to several dipsogenic stimuli, EB-treated rats have an increased daily water turnover apparently related to an inability to concentrate their urine. This in turn may be related to abnormalities in either synthesis or release of antidiuretic hormone or both.

scholarly journals Gut Microbiota Is Involved in Alcohol-Induced Osteoporosis in Young and Old Rats Through Immune Regulation

2021 ◽  
Vol 11 ◽  
Author(s):  
Ming Cheng ◽  
Bo Tan ◽  
Xiaojing Wu ◽  
Feng Liao ◽  
Fei Wang ◽  
...  
Keyword(s):  
Alcohol Consumption ◽  
Gut Microbiota ◽  
Bone Metabolism ◽  
Alcohol Metabolism ◽  
Excessive Alcohol Consumption ◽  
Young Rats ◽  
Age Related ◽  
Different Ages ◽  
Old Rats

Long-term and excessive alcohol consumption are risk factors for osteoporosis. Excessive drinking can reduce bone density and also cause imbalance of gut microbiota. And gut microbiota can affect bone metabolism through various mechanisms, and the regulation of gut microbiota is closely related to age. However, the effects of gut microbiota on alcohol-induced osteoporosis at different ages are unclear. In this study, young and old rats were used to induce osteoporosis by long-term alcohol consumption, and alcohol metabolism, bone morphology, bone absorption and immune activity of rats were analyzed to determine the effects of alcohol on rats of different ages. In addition, changes of gut microbiota in rats were analyzed to explore the role of gut microbiota in alcohol-induced osteoporosis in rats of different ages. The results showed the ability of alcohol metabolism was only associated with age, but not with alcohol consumption. Long-term alcohol consumption resulted in the changes of bone metabolism regulating hormones, bone loss, activation of receptor activator of NF-κB ligand (RANKL) signaling and inflammatory response. And osteoporosis was more severe in old rats than young rats, suggesting that alcohol-induced osteoporosis is age-related. In addition, long-term drinking also affected the composition of gut microbiota in rats, with a significant increase in the proportion of pro-inflammatory microorganisms. Overall, this study found that long-term alcohol consumption induced osteoporosis and affected the composition of gut microbiota. And alcohol can activate T lymphocytes directly or indirectly by regulating the changes of gut microbiota to produce cytokines, and further activate osteoclasts. In addition, the osteoporosis was more severe in the old rats than young rats, which may be due to the higher diversity and stronger regulation ability of gut microbiota in young rats compared with old rats.

Food intake, body weight, and adiposity in female rats: actions and interactions of progestins and antiestrogens

1981 ◽  
Vol 240 (5) ◽  
pp. E474-E481 ◽  
Author(s):  
J. M. Gray ◽  
G. N. Wade
Keyword(s):  
Body Weight ◽  
Adipose Tissue ◽  
Food Intake ◽  
Estradiol Benzoate ◽  
Female Rats ◽  
Antiestrogenic Activity ◽  
Ovx Rats ◽  
Increase Food Intake ◽  
Series Of Experiments ◽  
Adipose Tissue Lipoprotein Lipase

A series of experiments examined the effects of two progestins, progesterone and R 5020, and two nonsteroidal antiestrogens, nafoxidine and MER-25, on body weight and composition in female rats. Both progesterone and R 5020 increased food intake, body weight, and carcass adiposity in ovariectomized (OVX) rats treated with estradiol benzoate (EB), but neither progestin had any effect on these measures in OVX rats not treated with EB. R 5020 was substantially more effective than progesterone on all end points. Nafoxidine and MER-25 mimicked the actions of estradiol and decreased adipose tissue lipoprotein lipase (LPL) activity by 75–80%. For adipose tissue LPL activity, both nafoxidine and MER-25 were full estrogen agonists and without antiestrogenic activity. Nafoxidine also mimicked the effects of EB by reducing food intake, body weight, and carcass adiposity in OVX rats. In contrast, nafoxidine antagonized the induction of cytoplasmic progestin ([3H]R 5020) binding sites by EB in parametrial adipose tissue of OVX rats. In nafoxidine-treated OVX rats, concurrent progesterone administration had no effect on adipose tissue LPL activity, but progesterone did increase food intake, body weight, and carcass fat content. Some physiological mechanisms by which gonadal steroids may act to influence eating and adiposity are discussed.

scholarly journals Differential effects of aging on estrogen negative and positive feedback

2011 ◽  
Vol 301 (2) ◽  
pp. E351-E355 ◽  
Author(s):  
N. D. Shaw ◽  
S. S. Srouji ◽  
S. N. Histed ◽  
J. E. Hall
Keyword(s):  
Positive Feedback ◽  
Ovarian Function ◽  
Follicular Phase ◽  
Gonadal Steroids ◽  
Short Term ◽  
Ovarian Steroids ◽  
Age Related ◽  
Reproductive Axis ◽  
Effects Of Aging ◽  
Positive Feedback Effect

Recent studies have demonstrated an age-related decline in gonadotropins and a decrease in pituitary responsiveness to GnRH, indicating that aging influences the neuroendocrine components of the female reproductive axis independently of changes in ovarian function. To determine whether aging might also affect the luteinizing hormone (LH) negative and positive feedback responses to gonadal steroids, we administered a controlled, graded sex steroid infusion to 11 younger (45–56 yr) and nine older (70–80 yr) postmenopausal women (PMW) in whom endogenous ovarian steroids and peptides are uniformly low. The doses of estradiol (E2) and progesterone (P) were chosen to mimic levels across the normal follicular phase and have been shown previously to induce negative followed by positive feedback on LH. Similar E2 and P levels were achieved in younger and older PMW ( P = 0.4 and 0.3, respectively) and produced a biphasic LH response in all subjects. The early decline in LH to 53% of baseline was not different in older vs. younger PMW. However, the positive feedback effect was attenuated in older compared with younger PMW (peak LH 144.4 ± 19.5 vs. 226.8 ± 22.3 IU/l, respectively, P = 0.01). In conclusion, these studies in PMW demonstrate preservation of short-term steroid negative and positive feedback in response to exogenous E2 and P with aging. Attenuation of positive feedback in older compared with younger PMW is consistent with previous reports of declining GnRH responsiveness with aging.

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