Age-related changes of growth hormone secretory mechanisms in the rat pituitary gland

1991 ◽  
Vol 131 (2) ◽  
pp. 251-257 ◽  
Author(s):  
M. Parenti ◽  
D. Cocchi ◽  
G. Ceresoli ◽  
C. Marcozzi ◽  
E. E. Müller
Keyword(s):  
Growth Hormone ◽  
Male Rats ◽  
Lower Percentage ◽  
Aged Rats ◽  
Adult Rats ◽  
Infant Rats ◽  
Age Related ◽  
Rat Pituitary ◽  
Old Rats ◽  
Stimulation Of

ABSTRACT The mechanisms underlying the age-related decrease and increase in somatotroph responsiveness to growth hormone-releasing factor (GHRF) and somatostatin respectively were studied in rat pituitary membranes in vitro. Basal adenylate cyclase (AC) activity was similar in pituitary membranes from rats of 8 days (either sex) and male rats of 3 months, but it was almost threefold higher in membranes from male rats of 21–23 months. GHRF induced a lower percentage stimulation of AC activity in membranes from infant and old than adult rats. Somatostatin inhibited stimulation of AC induced by forskolin more effectively in membranes from adult than infant and old rats. In parallel experiments, since the tissue we used is formed by a mixed population of pituitary cells, we evaluated, for comparison, the effect on AC of neurohormones, i.e. vasoactive intestinal polypeptide (VIP) and dopamine which act primarily on lactotrophs. VIP induced a lower fold-stimulation of AC activity in membranes from infant and old than adult rats. Dopamine inhibited forskolin-induced stimulation of AC in the following rank order of magnitude: old, adult and infant rats, and was also more effective in inhibiting basal AC activity in old than in adult rats. The stimulatory and inhibitory G proteins (Gs and Gi) coupled to AC were measured indirectly by evaluating stimulatory and inhibitory effects of different concentrations of GTP on AC. GTP, at stimulatory concentrations, increased AC activity in membranes from infant and adult rats similarly whereas its effect was significantly greater in membranes from old rats. Conversely, GTP, at inhibitory concentrations, decreased AC activity similarly in membranes from adult and infant rats, whereas in old rats inhibition was apparent at more than a tenfold lower concentration of GTP. These data suggest (1) that the greater somatotroph sensitivity to GHRF in terms of GH secretion of the early postnatal period is not due to supersensitive GHRF receptors but rather may be accounted for, at least partially, by the low function of somatostatinergic receptors; (2) that the inability of GHRF to stimulate GH release in aged rats probably results from an uncoupling between the GHRF receptor and the G protein; and (3) that in aged rats the decreased ability of somatostatin to inhibit AC activity, in spite of the high Gi activity, results from a reduced number of somatotroph cells and, hence, receptors. Journal of Endocrinology (1991) 131, 251–257

Effect of Aging on the Activities of Acetylcholinesterase, Na+, K+-ATPase and Mg2+-ATPase in Rat Pituitary and Hypothalamus

1998 ◽  
Vol 53 (3-4) ◽  
pp. 168-172 ◽  
Author(s):  
Stylianos Tsakiris ◽  
Panagoula Angelogianni ◽  
John C. Stavridis
Keyword(s):  
Atpase Activity ◽  
Ache Activity ◽  
Energy Production ◽  
Metabolic Energy ◽  
Adult Rats ◽  
Neural Excitability ◽  
Age Related ◽  
Rat Pituitary ◽  
Old Rats

Abstract Acetylcholinesterase (AChE), Na+, K+-ATPase and Mg2+-ATPase activities were esti­mated in homogenised rat pituitary and hypothalamus of 4-and 22-month-old rats. AChE activity was not altered in the pituitary of aged com pared to adult rats, while it was found decreased by about 40% in the hypothalamus. Na+,K+-ATPase activity remained stable in the hypothalamus, while it was decreased by about 38% in the pituitary. Mg2+-ATPase activ­ity remained unchanged in the hypothalamus, but was increased by about 83% in the pitu­itary. This pituitary Na+, K+-ATPase inactivation may result in pathological mood and de­creased neural excitability and metabolic energy production in aged animals.The age-related alterations of AChE , Na+, K+-ATPase and Mg2+-ATPase activities may reflect changes in secretion and responses of some hormones of pituitary and hypothalamus.

Expression of acetylcholine receptor mRNAs in atrophying and nonatrophying skeletal muscles of old rats

1998 ◽  
Vol 85 (5) ◽  
pp. 1903-1908 ◽  
Author(s):  
Ronald R. Gomes ◽  
Frank W. Booth
Keyword(s):  
Skeletal Muscle ◽  
Acetylcholine Receptor ◽  
Biceps Brachii ◽  
Male Rats ◽  
Brown Norway ◽  
Mrna Levels ◽  
Adult Rats ◽  
Γ Subunit ◽  
Age Related ◽  
Old Rats

We examined the age-related association in skeletal muscle between atrophy and expression of mRNAs encoding both the γ-subunit of the nicotinic acetylcholine receptor (AChR), and myogenin, a transcription factor that upregulates expression of the γ-subunit promoter. Gastrocnemius and biceps brachii muscles were collected from young (2-mo-old), adult (18-mo-old), and old (31-mo-old) Fischer 344/Brown Norway F1 generation cross male rats. In the gastrocnemius muscles of old vs. young and adult rats, lower muscle mass was accompanied by significantly elevated AChR γ-subunit and myogenin mRNA levels. In contrast, the biceps brachii muscle exhibited neither atrophy nor as drastic a change in AChR γ-subunit and myogenin mRNA levels with age. Expression of the AChR ε-subunit mRNA did not change with age in either gastrocnemius or biceps brachii muscles. Thus changes in skeletal muscle AChR γ-subunit and myogenin mRNA levels may be more related to atrophy than to chronological age in old rats.

scholarly journals Decrease in the Sensitivity of Myocardium to M3 Muscarinic Receptor Stimulation during Postnatal Ontogenisis

Acta Naturae ◽  
2016 ◽  
Vol 8 (2) ◽  
pp. 127-131 ◽  
Author(s):  
S. V. Tapilina ◽  
D. V. Abramochkin
Keyword(s):  
Receptor Gene ◽  
Ventricular Myocardium ◽  
Muscarinic Agonist ◽  
Adult Rats ◽  
Age Related ◽  
Definite Effect ◽  
M3 Receptors ◽  
M3 Receptor ◽  
Old Rats ◽  
Stimulation Of

Type 3 muscarinic receptors (M3 receptors) participate in the mediation of cholinergic effects in mammalian myocardium, along with M2 receptors. However, myocardium of adult mammals demonstrates only modest electrophysiological effects in response to selective stimulation of M3 receptors which are hardly comparable to the effects produced by M2 stimulation. In the present study, the effects of selective M3 stimulation induced by application of the muscarinic agonist pilocarpine (10 M) in the presence of the selective M2 blocker methoctramine (100 nM) on the action potential (AP) waveform were investigated in isolated atrial and ventricular preparations from newborn and 3-week-old rats and compared to those in preparations from adult rats. In the atrial myocardium, stimulation of M3 receptors produced a comparable reduction of AP duration in newborn and adult rats, while in 3-week-old rats the effect was negligible. In ventricular myocardial preparations from newborn rats, the effect of M3 stimulation was more than 3 times stronger compared to that from adult rats, while preparations from 3-week old rats demonstrated no definite effect, similarly to atrial preparations. In all studied types of cardiac preparations, the effects of M3 stimulation were eliminated by the selective M3 antagonist 4-DAMP (10 nM). The results of RT-PCR show that the amount of product of the M3 receptor gene decreases with the maturation of animals both in atrial and ventricular myocardium. We concluded that the contribution of M3 receptors to the mediation of cardiac cholinergic responses decreases during postnatal ontogenesis. These age-related changes may be associated with downregulation of M3 receptor gene expression.

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

Regulation of parathyroid hormone secretion by plasma calcium in aging rats

1991 ◽  
Vol 260 (2) ◽  
pp. E220-E225 ◽  
Author(s):  
J. Fox
Keyword(s):  
Parathyroid Hormone ◽  
Hormone Secretion ◽  
Fold Increase ◽  
Male Rats ◽  
Aged Rats ◽  
Adult Rats ◽  
Dihydroxyvitamin D3 ◽  
Set Point ◽  
Skeletal Resistance ◽  
Immunoreactive Parathyroid Hormone

Plasma immunoreactive parathyroid hormone (irPTH) levels increase with aging. This study determined 1) whether NH2-terminal irPTH secretory responses to induced hypocalcemia differ between adult (6-mo-old) and aged (24- to 26-mo-old) male rats and 2) whether a higher set point for irPTH release by Ca is responsible for the elevated irPTH levels with aging. Basal irPTH levels were 68% higher and 1,25-dihydroxyvitamin D3 levels were 44% lower in aged rats. An acutely induced, constant hypocalcemic stimulus [0.32 mM decrement in ionized Ca (Ca2+) for 2 h] was developed in catheterized conscious adult and aged rats by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) infusion using the Ca clamp technique. The initial irPTH secretory response to acute hypocalcemia (5-10 min) was reduced in aged rats (1.9- vs. 3.1-fold increase), suggesting reduced hormone stores. However, higher sustained irPTH levels (30 min to 2 h) were maintained in aged rats, indicating increased irPTH synthesis and release. The EGTA infusion rate necessary to maintain constant hypocalcemia was less in aged rats, suggesting skeletal resistance to PTH. Slow EGTA and Ca infusions were used to determine irPTH secretion at plasma Ca2+ levels from 0.7 to 1.5 mM. In aged rats, irPTH levels were higher at all Ca2+ concentrations, but the set point for irPTH release by Ca2+ was the same as in adult rats. Thus the elevated irPTH secretion in aged rats is not caused by a change in the set point for irPTH release but does result in decreased irPTH stores.

Pituitary-adrenal response to bacterial endotoxin in developing rats

1988 ◽  
Vol 255 (4) ◽  
pp. E525-E530 ◽  
Author(s):  
L. Witek-Janusek
Keyword(s):  
Plasma Corticosterone ◽  
Neonatal Rat ◽  
Bacterial Endotoxin ◽  
Plasma Acth ◽  
Adult Rats ◽  
Age Related ◽  
Corticosterone Response ◽  
Adrenal Response ◽  
Old Rats ◽  
Related Pattern

The neonatal rat is very sensitive to the lethal effects of bacterial endotoxin. Because of the adaptive importance of pituitary-adrenal secretions to stress, this study examined the ontogeny of the plasma corticosterone and adrenocorticotropic hormone (ACTH) responses to endotoxin. The lethal sensitivity of young rats to endotoxin ranged from 0.5 to 30 mg/kg (ip) in the 1- to 21-day-old rat. After endotoxin treatment, the 1- and 2-day-old rat showed marked elevations of corticosterone similar in magnitude to that seen in 21-day-old and adult rats; however, significantly depressed corticosterone increments were observed in the 5-, 10-, and 14-day-old rats. This age-related pattern of adrenocortical secretion was correlated with the developing rat's corticosterone response to exogenous ACTH. In contrast, endotoxin administered to 5-, 10-, and 14-day-old rats resulted in increments of plasma ACTH similar to those observed in the 21-day-old and adult rats. Although plasma ACTH levels increased by 84-127% in the 1- and 2-day-old rats, these increases were significantly less than those of rats at all other ages tested. Thus the newborn rat mounts an effective corticosterone response to endotoxin, loses this ability between ages 5-14 days, and regains this response at 21 days of age. Because the hyporesponsive ages exhibit a marked increase in ACTH secretion, the loss of the adrenocortical response to endotoxin appears to be a result of a depressed responsiveness of the adrenal cortex to ACTH.

Effect of growth hormone on gastrocnemius muscle of aged rats after immobilization: biochemistry and morphology

1993 ◽  
Vol 75 (4) ◽  
pp. 1529-1535 ◽  
Author(s):  
E. Carmeli ◽  
Z. Hochberg ◽  
E. Livne ◽  
I. Lichtenstein ◽  
C. Kestelboim ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Gastrocnemius Muscle ◽  
Muscle Protein ◽  
Aged Rats ◽  
Muscle Weight ◽  
Hindlimb Muscles ◽  
Capillary Blood Volume ◽  
Rat Growth ◽  
Old Rats ◽  
Limb Immobilization

Immobilization of limbs of aged animals is associated with swift muscular damage and atrophy. We investigated the effect of rat growth hormone (rGH) on immobilized hindlimb muscles of 26-mo-old rats. Administration of rGH significantly reduced muscle weight loss and muscle protein oxidation caused by immobilization. Capillary blood volume, measured by photoplethysmography of the hindlimb, showed a 34% reduction in immobilized animals, which was eliminated by rGH. The activity of creatine phosphokinase in immobilized gastrocnemius muscle was significantly reduced by immobilization. This damage was diminished by rGH administration. Similarly, the increase in acid phosphatase activity in immobilized muscle was reduced after rGH treatment. Morphologically, marked muscle atrophy and fiber disorientation were observed in immobilized limbs. Therapy with rGH prevented some of these changes. These results indicate that administration of rGH may provide a useful means to attenuate the degenerative effects of limb immobilization of aged rats, as evident from physiological, biochemical, and morphological parameters.

scholarly journals Pairing Cholinergic Enhancement with Perceptual Training Promotes Recovery of Age-Related Changes in Rat Primary Auditory Cortex

2016 ◽  
Vol 2016 ◽  
pp. 1-18 ◽  
Author(s):  
Patrice Voss ◽  
Maryse Thomas ◽  
You Chien Chou ◽  
José Miguel Cisneros-Franco ◽  
Lydia Ouellet ◽  
...  
Keyword(s):  
Auditory Cortex ◽  
Structural Changes ◽  
Primary Auditory Cortex ◽  
Auditory Training ◽  
Tone Frequency ◽  
Perceptual Training ◽  
Adult Rats ◽  
Functional Changes ◽  
Age Related ◽  
Old Rats

We used the rat primary auditory cortex (A1) as a model to probe the effects of cholinergic enhancement on perceptual learning and auditory processing mechanisms in both young and old animals. Rats learned to perform a two-tone frequency discrimination task over the course of two weeks, combined with either the administration of a cholinesterase inhibitor or saline. We found that while both age groups learned the task more quickly through cholinergic enhancement, the young did so by improving target detection, whereas the old did so by inhibiting erroneous responses to nontarget stimuli. We also found that cholinergic enhancement led to marked functional and structural changes within A1 in both young and old rats. Importantly, we found that several functional changes observed in the old rats, particularly those relating to the processing and inhibition of nontargets, produced cortical processing features that resembled those of young untrained rats more so than those of older adult rats. Overall, these findings demonstrate that combining auditory training with neuromodulation of the cholinergic system can restore many of the auditory cortical functional deficits observed as a result of normal aging and add to the growing body of evidence demonstrating that many age-related perceptual and neuroplastic changes are reversible.

Age-related susceptibility to muscle damage following mechanotherapy in rats recovering from disuse atrophy

2021 ◽  
Author(s):  
Zachary R Hettinger ◽  
Kyoko Hamagata ◽  
Amy L Confides ◽  
Marcus M Lawrence ◽  
Benjamin F Miller ◽  
...  
Keyword(s):  
Older Adults ◽  
Muscle Mass ◽  
Older Adult ◽  
Recovery Period ◽  
Male Rats ◽  
Hindlimb Suspension ◽  
Disuse Atrophy ◽  
Adult Rats ◽  
Transverse Stiffness ◽  
Age Related

Abstract The inability to fully recover lost muscle mass following periods of disuse atrophy predisposes older adults to lost independence and poor quality of life. We have previously shown that mechanotherapy at a moderate load (4.5 N) enhances muscle mass recovery following atrophy in adult, but not older adult rats. We propose that elevated transverse stiffness in aged muscle inhibits the growth response to mechanotherapy and hypothesize that a higher load (7.6 N) will overcome this resistance to mechanical stimuli. F344/BN adult and older adult male rats underwent 14-days of hindlimb suspension, followed by 7-days of recovery with (RE+M) or without (RE) mechanotherapy at 7.6 N on gastrocnemius muscle. The 7.6 N load was determined by measuring transverse passive stiffness and linearly scaling up from 4.5 N. No differences in protein turnover or mean fiber cross sectional area were observed between RE and RE+M for older adult rats or adult rats at 7.6 N. However, there was a higher number of small muscle fibers present in older adult, but not adult rats, which was explained by a 16-fold increase in the frequency of small fibers expressing embryonic myosin heavy chain. Elevated central nucleation, satellite cell abundance, and dystrophin -/laminin + fibers were present in older adult rats only following 7.6 N, while 4.5 N did not induce damage at either age. We conclude that age is an important variable when considering load used during mechanotherapy and age-related transverse stiffness may predispose older adults to damage during the recovery period following disuse atrophy.

Kinetic impairment of nitrogen and muscle glutamine metabolisms in old glucocorticoid-treated rats

1999 ◽  
Vol 276 (3) ◽  
pp. E558-E564 ◽  
Author(s):  
Regine Minet-Quinard ◽  
Christophe Moinard ◽  
Françoise Villie ◽  
Stephane Walrand ◽  
Marie-Paule Vasson ◽  
...  
Keyword(s):  
Control Group ◽  
Synthetase Activity ◽  
Aged Rats ◽  
Sprague Dawley ◽  
Adult Rats ◽  
Glucocorticoid Treatment ◽  
Sprague Dawley Rats ◽  
End Of Treatment ◽  
Catabolic State ◽  
Old Rats

Aged rats are more sensitive to injury, possibly through an impairment of nitrogen and glutamine (Gln) metabolisms mediated by glucocorticoids. We studied the metabolic kinetic response of adult and old rats during glucocorticoid treatment. The male Sprague-Dawley rats were 24 or 3 mo old. Both adult and old rats were divided into 7 groups. Groups labeled G3, G5, and G7 received, by intraperitoneal injection, 1.50 mg/kg of dexamethasone (Dex) for 3, 5, and 7 days, respectively. Groups labeled G3PF, G5PF, and G7PF were pair fed to the G3, G5, or G7 groups and were injected with an isovolumic solution of NaCl. One control group comprised healthy rats fed ad libitum. The response to aggression induced specifically by Dex (i.e., allowing for variations in pair-fed controls) appeared later in the aged rats (decrease in nitrogen balance from day 1 in adults but only from day 4 in old rats). The adult rats rapidly adapted to Dex treatment, whereas the catabolic state worsened until the end of treatment in the old rats. Gln homeostasis was not maintained in the aged rats; despite an early increase in muscular Gln synthetase activity, the Gln pool was depleted. These results suggest a kinetic impairment of both nitrogen and muscle Gln metabolisms in response to Dex with aging.

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