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3 concentration in HSpp animals is associated by reduction of the stress defense enzymes TST, PRDX3, PRDX6, ETHE1 and also CAT, strongly suggesting the involvement of T 3 - and THRA-mediated signaling in this adaptation process. Downregulation of
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Wyrwoll CS Smith JT Yap C Clarke MW Waddell BJ 2016 Pregnancy-induced adaptations of the central circadian clock and maternal glucocorticoids . Journal of Endocrinology 228 135 – 147 . ( https://doi.org/10
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cortical and cancellous bone parameters observed in the course of treatments (5 vs 10 weeks) not only in treated groups but also in untreated SF group may be explained by the adaptation mechanisms to the potentially negative effect of osteoporosis
Laboratory of Animal Nutrition,
Laboratory of Animal Breeding, Department of Animal Science, Agricultural University of Athens, 75, Iera odos, 11855 Athens, Greece
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Laboratory of Animal Nutrition,
Laboratory of Animal Breeding, Department of Animal Science, Agricultural University of Athens, 75, Iera odos, 11855 Athens, Greece
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Laboratory of Animal Nutrition,
Laboratory of Animal Breeding, Department of Animal Science, Agricultural University of Athens, 75, Iera odos, 11855 Athens, Greece
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Laboratory of Animal Nutrition,
Laboratory of Animal Breeding, Department of Animal Science, Agricultural University of Athens, 75, Iera odos, 11855 Athens, Greece
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Laboratory of Animal Nutrition,
Laboratory of Animal Breeding, Department of Animal Science, Agricultural University of Athens, 75, Iera odos, 11855 Athens, Greece
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Laboratory of Animal Nutrition,
Laboratory of Animal Breeding, Department of Animal Science, Agricultural University of Athens, 75, Iera odos, 11855 Athens, Greece
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Laboratory of Animal Nutrition,
Laboratory of Animal Breeding, Department of Animal Science, Agricultural University of Athens, 75, Iera odos, 11855 Athens, Greece
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disease in adult life. Lancet 341 938 –941. Bispham J , Gopalakrishnan GS, Dandrea J, Wilson V, Budge H, Keisler DH, Broughton Pipkin F, Stephenson T & Symonds ME 2003 Maternal endocrine adaptation throughout pregnancy to
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SUMMARY
The effect of oral administration of betamethasone (25 μg kg−1 day−1) on the duodenal absorption of calcium has been studied in chicks using the ligated loop technique in vivo. The chicks were fed normal calcium, normal phosphorus (NCaNP), low calcium, normal phosphorus (LCaNP) or normal calcium, low phosphorus (NCaLP) diets. Daily oral administration of betamethasone for 2–3 weeks markedly reduced the absorption of calcium in chicks fed the NCaNP diet, but did not significantly affect the adaptation in absorption when the NCaLP or LCaNP diets were fed for the same period of time. In one group of chicks, betamethasone was administered daily for 10 days before the birds were transferred to the NCaLP or LCaNP diets. Adaptation was again unaffected by betamethasone treatment. Administration of betamethasone caused a marked retardation in growth-rate, hypercalcaemia and an increased percentage of ash in the tibiae.
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ABSTRACT
The effect of hypothyroidism on potassium adaptation (shown by increased potassium secretion in response to potassium loading) and on the action of aldosterone on potassium secretion and sodium fluxes was examined in the rat distal colon.
Potassium adaptation, particularly the response to an acute potassium load, was impaired by hypothyroidism which also considerably reduced the rise of transepithelial electrical potential difference (p.d.) of total and transcellular (active) lumen-to-plasma sodium fluxes and of potassium secretion normally produced by aldosterone. These changes were, in part, corrected by a short period (3 days) of tri-iodothyronine replacement. Moreover in aldosterone-treated hypothyroid rats, amiloride in the lumen was considerably less effective in reducing the p.d. and sodium fluxes than in aldosterone-treated normal rats.
The intracellular sodium transport pool was greater in the hypothyroid than in the normal rats (5·0± 1·1 (s.e.m.) nmol/mg dry weight compared with 2·9 ± 0·2 nmol/mg dry weight; P<0·02). Aldosterone increased the pool in the normal but not in the hypothyroid rats while amiloride had little effect on the pool in the aldosterone-treated hypothyroid rats but almost abolished it in aldosterone-treated normal rats.
Aldosterone plays a major part in the adaptation of colonic sodium and potassium transport to sodium depletion or potassium excess; these adaptations were much impaired in hypothyroid animals. The present results are consistent with a deficiency in aldosterone induction of potassium- and amiloride-sensitive sodium pathways in the apical membrane of colonic epithelial cells in hypothyroid rats, a deficiency which limits the stimulant effect of aldosterone on sodium and potassium transport.
Journal of Endocrinology (1990) 124, 47–52
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SUMMARY
The phenomenon of adaptation of intestinal calcium absorption to changes in dietary calcium has been studied in conscious pigs with Thiry–Vella jejunal loops. The result of decreasing the calcium content of the diet from 1·2 to 0·1% was an increase in the efficiency of the net absorption of calcium from the fluid used to perfuse the jejunal loop; this increase took place 4–6 days after the change in diet. A similar effect was noted in four pigs which had previously been parathyroidectomized and in two thyroparathyroidectomized pigs with thyroxine replacement therapy. The effect seen in the parathyroidectomized animals was not attributable to an increase in the concentration gradient of calcium ions between the jejunal lumen and the blood after the change to the low calcium diet. There was a marked increase in the amount of calcium-binding protein in the mucosa taken from the distal three-quarters of the small intestine of intact pigs fed a low calcium diet. However, after parathyroidectomy, the level of calcium in the diet had no significant effect on the amount of calcium-binding protein in the small intestine.
It is concluded that, in pigs, neither parathyroid hormone nor calcitonin is necessary for intestinal adaptation to a low calcium diet and that, although this adaptation may be mediated by 1,25-dihydroxycholecalciferol, a significant increase in the level of calcium-binding protein in the intestine is only seen when the parathyroid glands are intact.
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ABSTRACT
Plasma thyroxine (T4) concentrations were measured during pregnancy and lactation in goats on diets with different energy concentrations to study the role of T4 secretion in metabolic adaptation to pregnancy and lactation. Thyroxine distribution space (the volume of fluid required to dissolve the total pool of circulating T4 at a concentration equal to that in the plasma) and secretion rates were determined by using 125I-labelled T4 at different stages of lactation and pregnancy.
Plasma concentrations of T4 increased during lactation and reached maximum levels 4–5 months after giving birth. They then remained fairly constant for the following 2–3 months until the goats became pregnant again. Thyroxine concentrations decreased slightly during pregnancy and showed a sudden drop at the onset of lactation. Minimum concentrations were observed during the first 2–3 weeks of lactation after which time concentrations increased slowly. Average concentrations for goats on a low-energy diet were consistently lower than those in goats on a high-energy diet. The mean secretion rate was 10·4 nmol day−1 kg body wt−0·75. The distribution spaces were much lower than the total extracellular space. The average distribution space in non-pregnant and pregnant goats was 11 and 5·3% of the body weight respectively.
The decrease in T4 secretion rate and T4 distribution space during pregnancy is considered to be part of a homeorhetic adaptation to the condition. The drop in T4 secretion rate at the onset of lactation appears to be a homeostatic adaptation to a decreased fuel supply, similar to the situation with fasting or energy malnutrition.
J. Endocr. (1985) 107, 421–427
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ABSTRACT
The ability of insulin-like growth factor-I (IGF-I), insulin and GH to promote hypoosmoregulatory ability was examined in juvenile rainbow trout (Oncorhynchus mykiss). Following adaptation to 12 parts per thousand (p.p.t.) seawater for 5 days, fish were given a single injection of hormone or vehicle, then exposed to 29 p.p.t. for 24 h and examined for changes in plasma osmolarity, ions and glucose. Ovine GH (oGH; 0·2 μg/g) significantly improved the ability of rainbow trout to maintain plasma osmolarity and sodium levels following transfer to 29 p.p.t. seawater. Recombinant bovine IGF-I (0·01, 0·05 and 0·2 μg/g) also improved the hypoosmoregulatory ability of trout; the effect being dose-dependent and greater than that of oGH. Bovine insulin (0·01, 0·05 and 0·2 μg/g) had no statistically significant effect on plasma ions. The results indicate that IGF-I is a potential mediator of the action of GH in seawater adaptation of salmonids.
Journal of Endocrinology (1991) 130, 87–92
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The photoperiodic mammal undergoes quite remarkable changes in physiology as part of its natural adaptations to seasonal fluctuations in the environment. Changes in energy balance and body weight are among these adaptations. In some seasonal mammals, such as the Siberian hamster (Phodopus sungorus), these changes in body weight have been explored in detail, and there is evidence for tightly controlled systems of energy balance that are coordinated by photoperiod acting via the temporal pattern of melatonin secretion from the pineal gland. The pathways and systems involved appear to be quite distinct from the hypothalamic pathways identified to regulate energy balance in studies of both mice and rats thus far. Instead it appears that in the Siberian hamster a tightly regulated system under the control of photoperiod is able to reset the tone of the systems involved in energy balance regulation. Understanding how photoperiod and melatonin act within the hypothalamus to regulate energy balance offers potentially fundamental and important new insights into the control of energy balance. This review describes the current state of our knowledge.
