Injection Of Thyroxine Research Articles

Effects of temperature acclimation and thyroxine injection on glycogen storage and oxygen consumption in the frog, Rana tigrina

1. 1. The effects of temperature acclimation and thyroxine injection (at 2 μg/10g body wt/day for 7 days) on the oxygen consumption and glycogen storage of the liver tissue in the adult Rana tigrina were investigated at 15 and 25°C. 2. 2. The mean values of oxygen consumption were 0.127 and 0.251 μ1 O 2/mg/hr and the hepatic glycogen were 30.22 and 27.36 mg/g wet wt in the control frogs at 15 and 250°C, respectively. 3. 3. In thyroxine-treated frogs, there was an increase of 25% in oxygen consumption and a decrease of 125% in the hepatic glycogen at 25°C, but there were no significant differences at 15°C, compared with the controls. 4. 4. It is concluded that the metabolic activity, and the effect of thyroxine thereon, of R. tigrina is dependent on the environmental temperature.

Effect of thyroxine and analogs on protein and nucleic acid contents of liver and muscle of Lata fish ( Ophicephalus punctatus)

Injection of thyroxine (T 4) induced a change, biphasic in nature, in the amounts of protein and RNA in liver and muscle of Lata fish ( Ophicephalus punctatus). The lower doses of T 4 (0.5 μg/g, three injections; or 1 μg/g, single injection) increased and the higher doses (2 or 4 μg/g, single injection) decreased the amounts of protein and RNA in liver and muscle on the fourth or fifth day after injection. The enhanced or reduced levels of liver protein and RNA with 1 or 4 μg of T 4/g, respectively, continued up to the 12th day after injection. The muscle protein and RNA levels at 1 or 2 μg of T 4/g were not different from the control values on the 12th day, whereas the reduced level of only muscle protein (not RNA) with 4 μg of T 4/g remained unchanged up to the 12th day. A single injection of tetraiodothyroacetic acid (TETRAC, 1, 2, or 4 μg/g) increased the protein and RNA contents of liver and muscle in Lata fish. The increased levels of these substances continued up to the 12th day after injection, except in muscle at a dose of 1 μg/g. Triiodothyroacetic acid (TRIAC, 2 or 4 μg/g, single injection) also enhanced the amounts of protein and RNA in liver and muscle. This enhanced level of these cellular substances was also observed on the 12th day at a dose of only 4 μg of TRIAC/g. DNA contents of both liver and muscle remained unaltered at all doses of T 4, TETRAC, and TRIAC used.

Effect of Hormones on the Development of Creatine Kinase Activity in Rat Skeletal Muscle

Various approaches have been used in order to determine whether or not a certain hormone is a stimulus for the development of the muscle-specific enzyme, creatine kinase. Both thyroxine and glucocorticoids can be considered as naturally occurring stimuli for the synthesis of creatine kinase. The maximum increase of creatine kinase activity after stimulation by glucocorticoids (about 25%) occurs between 5 and 7 days after birth. A single injection of thyroxine has virtually no effect during this period. However, when a pretreatment with thyroxine is given, cortisone acetate administration increases creatine kinase activity to about 155%. The effect of cortisone acetate is due to de novo synthesis of creatine kinase. The augmentation of the effect of cortisone acetate by thyroxine is dependent on DNA synthesis. Thyroxine administration apparently causes the formation of more competent muscle cells. The effects of both hormones are age-dependent. Thyroxine and cortisone acetate administration to fetuses can prematurely evoke to MM isoenzyme of creatine kinase. Both hormones probably play a role in the activation of the M gene during embryonic development. Sex hormones are able to influence neither creatine kinase activity nor muscle growth. However, castration of male rats immediately after birth causes an impairment of growth at older ages. The androgen production by the testes immediately after birth seems to be of main importance for body growth development. It can be concluded from these results that creatine kinase in muscle is under multiple hormonal control, just as is observed for a number of enzymes in other tissues.

Metabolic response to thyroxine in the newborn pig.

The oxygen consumption rate (ml O2/kg/min), the pulse rate, respiratory frequency and body temperatures were measured after a single subcutaneous injection of thyroxine (80 micrograms/kg) or adrenaline (200 micrograms/kg) in unfasted pigs aged 1--11 days. Thyroxine produced a metabolic response after a latent period and potentiated the metabolic action of adrenaline. As reported in the literature, the existence of an immediate metabolic response to thyroxine was not evidenced. The obtained results support the view that in the newborn pig the physiological rise in metabolism which leads to metabolic stability might be caused by thyroxine, whose free fraction and highest level in the blood occurs shortly after birth. Potentiation of adrenaline action by thyroxine can contribute to this process.

Synaptosomal [125I]triiodothyronine after intravenous [125I]thyroxine.

We administered [125I]thyroxine intravenously to adult male rats and measured uptake and subcellular distribution of the hormone and its metabolites in brain. Fractional brain uptake decreased after a large dose of iodothyronine, providing evidence for saturability of the uptake mechanism. Well-defined patterns of regional and subcellular labeling were noted within 1 h after [125I]thyroxine injection. Radioactivity in synaptosomes was always greater than in any other particle separated per gram of brain, increasing linearly relative to radioactivity in brain cytosol during the 1st h. Although [125I]triiodothyronine derived from [125I]thyroxine was not identified in serum at any time interval, it was measurable in synaptosomes within 20 min and in brain cytosol within 1 h after labeled hormone administration. Concentrations of the radioactive metabolite were twofold greater and ratios of [125I]triiodothyronine to [125I]thyroxine concentration were threefold greater in synaptosomes than in cytosol. Therefore, thyroxine may be converted to triiodothyronine within nerve terminals. Synaptosomal localization of iodothyronines and their metabolites may be relevant to the marked central and peripheral adrenergic nervous system effects of these aromatic amino acid hormones.

Experimental hyperthyroidism in rats suppresses in vitro prostaglandin metabolism in lung and kidney

Metabolism of prostaglandin (PG) F2α and PGE2 was depressed 40–62% in 100,000 g cytoplasmic supernatants of lungs and kidneys prepared from rats made hyperthyroid by 18 daily L(-) thyroxine injections (200μg,s-c). These hyperthyroid rats had elevated serum thyroxine levels, cardiac hypertrophy and thyroid atrophy. There were no differences in soluble protein concentrations, NAD + utilisation by endogenous enzymes and substrates, or in the NAD + dependence of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) between the supernatants prepared from hyperthyroid rats and saline-injected controls. Thyroxine did not inhibit PG metabolism in vitro up to 260 μM. These results suggest that thyroxine specifically decreases intracellular levels of PG-metabolising enzymes, especially of the rate-limiting 15-PGDH. Metabolism of PGF2α and PGE2 by 15-PGDH was faster in smaller rats and declined with increasing animal weight. These studies imply that some of the clinical features of hyperthyroidism in man might be caused by deficiencies in PG metabolism.

Behavioural, electrocortical and body temperature effects after intracerebral infusion of TRH in fowls

In fowls TRH given into the III cerebral ventricle (0.25–5 μg) produced intense behavioural stimulation, electrocortical desynchronization and a slight increase in body temperature. In particular, an intense pattern of stereotyped head-neck movements, increase in locomotor activity, repeated and preening, vocalization, erection of the tail feathers and occasionally ‘escape responses’ were observed. This picture lasted for about 30 min and was followed by slight behavioural sedation during which stereotypies continued to occur but to a lesser extent. Similar increases in locomotor activity and stereotypies were evoked by infusing TRH into the hypothalamus whereas the unilateral microinfusion into the n. basalis or the n. mesencephalicus profundus, homologous to the mammalian striatum and s. nigra respectively, produced very intense stereotyped head-neck movements, wet-dog syndrome and vocalization. TRH given into the other areas of the brain (e.g. hyperstriatum, neostriatum, olfactory ventricle, eminentia basalis and lateral part of the mesencephalon) lacked effects on behaviour and body temperature. The effects of intraventricular infusion of TRH were antagonized by prior administration of haloperidol and spiperone whereas antagonists at α and β-adrenoceptors and at 5-HT receptors were ineffective. In addition, TRH reversed sedation induced by intraventricular α-methyl-p-tyrosine. Behavioural and body temperature effects of TRH were independent of its endocrine properties since these were not observed after systemic or intracerebroventricular injection of thyrotropin, triidothyronine and thyroxine. The increase in body temperature evoked by intracerebroventricular injection of TRH was due to activation of heat production and decrease in thermodispersive mechanisms.

Alprenolol fails to antagonize the metabolic changes following repeated thyroxine injections in the rat.

Repeated injections of rat with 1-thyroxine (50 microgram/kg daily for 5 five-day weeks) retarded the weight gain of the animals and increased the absolute and relative size of the heart, adrenals and interscapular brown adipose tissue. In the myocardium and thigh muscle, thyroxine treatment resulted in elevated activity of oxidative enzymes, succinate dehydrogenase, malate dehydrogenase and citrate synthase, while the activities of glycolytic enzymes remained unchanged. Glycogen content of the heart was decreased following thyroxine regime. In the brown fat, on the other hand, thyroxine injections resulted in a reduction of the activity of oxidative enzymes. This reduction can be accounted for by the decreased protein (enzyme) content of the tissue due to deposition of fat. Furthermore, thyroxine treatment delayed the body cooling of the rats swimming in water at 25 degrees C and enhanced hyperthermic response to injected noradrenaline. All these changes, which were not observable in rats treated with daily alprenolol (20 mg/kg) injections, were as pronounced in rats injected with alprenolol together with thyroxine as in rats injected with thyroxine only. It is concluded that beta blockers do not antagonize the metabolic changes due to hyperthyroidism.

Contributions of Plasma Triiodothyronine and Local Thyroxine Monodeiodination to Triiodothyronine to Nuclear Triiodothyronine Receptor Saturation in Pituitary, Liver, and Kidney of Hypothyroid Rats

Injections of triiodothyronine (T(3)) and thyroxine (T(4)) into chronically hypothyroid rats were used to evaluate the contribution of intracellular T(4) to T(3) conversion to nuclear T(3) in pituitary, liver, and kidney, and to correlate the occupancy of pituitary nuclear T(3) receptors with inhibition of thyroid-stimulating hormone (TSH) release. Injection of a combination of 70 ng T(3) and 400 ng T(4)/100 g body wt resulted in plasma T(3) concentrations of 45+/-7 ng/dl (mean+/-SD) and 3.0+/-0.4 mug/dl T(4) 3 h later. At that plasma T(3) level, the contribution of plasma T(3) to the nuclear receptor sites resulted in saturation of 34+/-7% for pituitary, 27+/-5% for liver, and 33+/-2% for kidney. In addition to the T(3) derived from plasma T(3), there was additional T(3) derived from intracellular monodeiodination of T(4) in all three tissues that resulted in total nuclear occupancy (as percent saturation) of 58+/-11% (pituitary), 36+/-8% (liver), and 41+/-11% (kidney), respectively. The percent contribution of T(3) derived from cellular T(4) added 41% of the total nuclear T(3) in the pituitary which was significantly higher than the contribution of this source in the liver (24%) or the kidney (19%). 3 h after intravenous injection of increasing doses of T(3), the plasma T(3) concentration correlated well with both the change in TSH and the nuclear occupancy, suggesting a linear relationship between the integrated nuclear occupancy by T(3) and TSH release rate. The contribution of intrapituitary T(4) to T(3) conversion to nuclear T(3) was accompanied by an appropriate decrease in TSH, supporting the biological relevance of nuclear T(3). Pretreatment of the animals with 6-n-propylthiouracil before T(4) injection decreased neither the nuclear T(3) derived from intrapituitary T(4) nor the subsequent decrease in TSH. These results indicate that intracellular monodeiodination of T(4) contributes substantially to the nuclear T(3) in the pituitary of the hypothyroid rat, and suggest a linear inverse relationship between nuclear receptor occupancy by T(3) in the pituitary and TSH release rate. The data further indicate that T(4) to T(3) monodeiodination is considerably more important as a source of nuclear T(3) in the pituitary than in the liver and kidney. This provides a mechanism whereby the TSH secretion could respond promptly to a decrease in thyroid secretion (predominantly T(4)) before a decrease in plasma T(3) would be expected to lead to significant metabolic hypothyroidism.

Thyroid hormone effects on protein and RNA metabolism in the rat anterior pituitary

Thyroidectomy reduced the incorporation of [ 3H]amino acids into total rat pituitary proteins as well as into electrophoretic fractions corresponding to growth hormone (GH) and prolactin. A single injection of thyroxine (200 μg/kg) reversed the effects of thyroidectomy on the GH (12 h) and prolactin (36 h) fractions. Evidence for a general increase in the rate of pituitary protein synthesis following this treatment was less conclusive, but two injections of the hormone had a definite stimulatory effect. [ 3H]Uridine uptake by the pituitary and its incorporation into RNA were elevated for 2 weeks after thyroidectomy. Thyroxine failed to suppress these changes for at least 36 h after injection. Actinomycin D (400 μg/kg) inhibited pituitary RNA synthesis and blocked the stimulatory effect of thyroxine on amino acid incorporation into the GH fraction. These results indicate that thyroid hormones: (1) promote pituitary protein synthesis, probably as a consequence of their effects on somatotrophs and lactotrophs; (2) exert a stimulatory effect on GH synthesis by affecting transcription.

Precocious decrease of chymotrypsinogen by thyroxine in the pancreas of suckling mice

Chymotrypsinogen activity in mouse pancreas gradually decreased from birth, reaching the adult level on day 20 after birth. In suckling mice the enzyme activity was decreased to 1 9 of the control value by injection of thyroxine. The activity was not affected by insulin, and was slightly increased, rather than decreased, by daily injection of hydrocortisone. The effect of thyroxine seemed to be direct, not due to modification of adrenal function.

Precocious differentation of mouse parotid glands and pancreas induced by hormones

Changes of α-amylase activity (1,4- α-D-glucan glucanohydrolase, EC 3.2.1.1) in mouse parotid gland pancreas were investigated during embryonic and postnatal development. Amylase activity in the parotid gland increased from around day 12 and reached the adult level on day 30. On the other hand, the activity in the pancreas increased during the last stage of gestation, decreased after birth, and then gradually increased from around day 15, reaching the adult level on day 35. Precocious differentiation of the parotid gland was induceed by injections of hydrocortisone or thyroxine after birth, but these hormones did not have additive effects on the parotid gland. Injection of insulin had little effect when given alone, but suppressed the effects of the other two hormones on the gland. Only hydrocortisone increased the amylase activity in mouse pancreas during postnatal development, the other two hormones causing slight decrease in pancreatic amylase. Adrenalectomy and injection of hydrocortisone affected the parotid gland but not the pancreas of adult mice. These results suggest that hydrocortisone involved in cytodifferentiations of the parotid gland and pancreas, and in maintenance of the parotid gland. Thyroxine may also be important in differentiation of the parotid gland.

Pituitary Nuclear 3,5,3′-Triiodothyronine and Thyrotropin Secretion: An Explanation for the Effect of Thyroxine

An excellent correlation was observed between nuclear triiodothyronine (T3) and the ensuing suppression of thyrotropin (TSH) after a single intravenous injection of T3 to thyroidectomized (hypothyroid) rats. At 1 and 2 hours after injection of thyroxine (T4), in amounts equally potent to the administered T3 in terms of acute suppression of TSH, the same quantities of T3 were found in the pituitary nuclei. Virtually no nuclear T4 was present, and plasma T3 was negligible at these short intervals after T4 injection. These results suggest that suppression of TSH release in hypothyroid rats occurs by interaction of T3 with the nuclear receptor of the thyrotroph. After T4 injection, the T3 found in the nucleus is derived from rapid intrapituitary monodeiodination.

Modification of 1,1-dichloroethylene hepatotoxicity by hypothyroidism

Exposure of fasted male rats for 4 hr to 2000 ppm of 1,1-dichloroethylene (1,1-DCE), which decreases hepatic contents of reduced glutathione (GSH), resulted in severe liver injury by 2 hr as manifested by morphologic and histochemical (i.e., Ca and glucose-6-phosphatase) alterations, elevation of serum alanine-α-ketoglutarate transaminase activity, increases in hepatic contents of Na and Ca, and decreases in K and Mg. Thyroidectomy, which increases hepatic amount of GSH, and, to a lesser extent, administration of antithyroid drugs minimized each parameter of liver injury while thyroxine injection to thyroidectomized animals restored susceptibility to 1,1-DCE. Three-day survival experiments demonstrated that thyroidectomy abolished the mortality and significantly decreased the total extent of hepatic necrosis caused by 1,1-DCE. Elevated concentrations of reduced GSH in the livers of the hypothyroid animals may be a factor in their resistance to this reactive molecule.

Thyroid control over biomembranes: Rat liver mitochondrial inner membranes

The effects of hypothyroidism and one injection of l-thyroxine on oxidative phosphorylation and the composition of proteins and phospholipids were examined in vesicles prepared from rat liver mitochondria by digitonin extractions. At 30 °C, the rates of ADP phosphorylation in sites I and II were below normal, and Mg 2+-ATPase activity was greater than normal in vesicles from hypothyroid rats. At temperatures below 20 °C and above 30 °C, the Mg 2+-ATPase was not accelerated above normal rates, a feature of temperature dependence shared by ADP phosphorylation (Chen, Y.-D. I., and Hoch, F. L., 1976, Arch. Biochem. Biophys. 172, 741–744). Respiration at 30 °C was undiminished in hypothyroid vesicles, as were the flavin and cytochrome contents, and thyroxine administration corrected the phosphorylation rate at 30 °C in 3 days without changing either respiration or electron-carrier contents. The 30 °C phosphorylation defect comprised a decreased V and K m for ADP and a decrease in the number of phosphorylating sites (measured with oligomycin) that accounted for most of the decreased phosphorylation rates, either dependent on or independent of the adenine nucleotide carrier. Vesicles from hypothyroid rats were not detectably depleted in major protein subunits, but were abnormal in phospholipid fatty acid contents. Thyroxine injection corrected the low unsaturation index of the fatty acids and the membrane contents of linoleic acid and its fatty acyl metabolites. Hypothyroidism appears to affect oxidative phosphorylation through the altered inner membrane lipid environment, which implies that previously reported direct, reversible effects of thyroxine may mimic repletion of the membranes with unsaturated fatty acyl groups.

Precocious induction of secretory granules by hormones in convoluted tubules of mouse submandibular glands.

Precocious differentiation of convoluted tubules of the submandibular glands of mice was induced by daily injection of thyroxine, insulin, hydrocortisone and 5alpha-dihydrotestosterone from day 4 after birth. This treatment induced enlargement of the tubules and synthesis of secretory granules in the tubules. Treatment with 5alpha-dihydrotestosterone alone had no effect on enlargement of the tubules or synthesis of the granules. These findings suggest that, besides androgenic hormones, these three hormones are also involved in synthesis of granules in developing mice.

Intra-amniotic injection of thyroxine (T4) to a human fetus: Evidence for conversion of T4 to reverse T3

131I (150 mCi) was inadvertently given to a woman during week 10 to 11 of her gestation. When referred, fetal size was estimated at 31 to 32 weeks' gestation. Because of the potential risk of fetal hypothyroidism, an amniocentesis, with an injection of 500 μg of thyroxine, was performed weekly from week 33 until delivery. T4, T3, thyroid-stimulating hormone (TSH), and rT3 were measured in amniotic fluid samples obtained at 33, 36, and 37 weeks. Maternal serum T4 was measured on the day of delivery. T4, T3, and TSH concentrations were measured in cord blood and during the neonatal period. The concentration of T4 in amniotic fluid (AF) was within the normal range at 32 weeks (prior to thyroxine); AF T3 and TSH were not detectable. The concentration of AF rT3 at 32 weeks also was normal (160 ng. per deciliter) and increased markedly after beginning intra-amniotic T4 injections; AF T4 increased modestly, but the AF T3 level remained unmeasurable. The concentration of T4 in cord serum, obtained within 24 hours of the last amniotic fluid thyroxine injection, was in the hyperthyroid range and the TSH level was low. The cord serum T3 level was at the upper range of normal. The infant's serum T4 and T3 both increased during the first 24 hours. The male infant developed normally and serum T4 and TSH concentrations were normal at 4 months of age. The data indicate: (1) that T4 injected into AF is absorbed by the human fetus, (2) that AF rT3 concentration increases markedly after the AF T4 injection, whereas AF T3 levels do not increase, and (3) that the neonatal TSH surge is not entirely suppressed by hyperthyroid levels of cord serum T4.

Effects of prolactin on the water and sodium content of larval tissues from neotenic and metamorphosing Ambystoma tigrinum

Neotenic tiger salamanders ( Ambystoma tigrinum) were injected with ovine prolactin (PL) or saline for 20 days. PL-treated animals had significantly greater gill lengths, tail heights, and wet body weights than controls. Analysis of the tail revealed that PL increased the content of water and sodium ion in that tissue. Serum sodium was unaffected by PL. Similarly, PL failed to alter the water content, sodium level, or dry weight of liver tissue. In neotenes induced to metamorphose with a single injection of thyroxine (T4), the simultaneous injection of a single dose of PL was able to slow gill and tail fin resorption. This effect could be correlated with reduced water loss by gill and tail tissue from animals receiving PL along with T4. In contrast, liver water content was not affected by PL during metamorphosis. These results are discussed with regard to the action of PL on growth, development, and osmoregulation in larval amphibians.

Effects of thyroid hormones on the evolution of monoamine oxidase activity in the brain and heart of the developing rat.

The evolution of monoamine oxidase (MAO) activity towards tryptamine has been studied from birth to 20 days post-natal in the brain and heart of male rats. Hyperthyroidism was induced by thyroxine injections and hypothyroidism by PTU administration. The results are expressed per unit of fresh weight and per unit of protein weight. Cardiac MAO is higher in the hyperthyroid animals than in controls as soon as 5 days following birth; the difference between the 2 groups increases until 20 days. The deficiency in thyroid hormones, on the other hand, was followed by a slight decrease in the cardiac enzyme, this decrease reflecting the general deficit in protein synthesis. Brain MAO is not affected by hyperthyroidism, but a clear deficit follows PTU administration. This deficit is significant beginning at 10 days and the difference between the 2 groups increases up to 20 days. The effects of PTU-induced hypothyroidism can be corrected by thyroxine injections. Except for the decrease in the level of cardiac enzyme in hypothyroid animals, all the effects on MAO activity are independent of the total protein content of both organs.

Thermoregulatory effects of peripheral catecholamines on the pigeon after treatment with thyroxine or thiouracil

1. Adult pigeons of both sexes were treated either with thyroxine (75 μg/kg), thiouracil (3 mg/kg) or saline (0.85% NaCl) every two days for three weeks either at 22°C or at 2°C. 2. The thermoregulatory effect of peripherally injected NA (1–3 mg/kg) was tested both at 6°C and at 32°C. In pigeons after repeated thyroxine-handling NA caused more marked hypo- or hyperthermia at 6°C or at 32°C, respectively, than after thiouracil-handling. 3. Repeated injections of thyroxine or thiouracil elevated plasma glucose level at 22°C, but not at cold. No significant changes in lipolytic activity were seen after three week's handlings. 4. All examined tissues of thyroxine-handled pigeons seemed to consume more oxygen in vitro than those of thiouracil-handled, also they seemed to be more sensitive to added NA (10 −4 M) than those of thiouracil-ones. 5. The results show that thyroxine (still augmented after cold-acclimation) potentiates the hypo- or hyperthermic effects of NA below or above the thermoneutral zone. This effect is counteracted by thiouracil.