The Action of Thyroid Hormone

Bernal, Juan; Refetoff, Samuel

doi:10.1111/j.1365-2265.1977.tb03319.x

Cited by 104 publications

(28 citation statements)

References 126 publications

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“…While these effects are well recognized, the mechanism by which thyroid hormone influences these processes has remained largely a matter of speculation (20). The recent demonstration of a specific nuclear T3 receptor in various tissues (21)(22)(23), coupled with work indicating that treatment with thyroid hormone increases polymerase (24) or chromatin template activity (25) and the poly(A)-rich fraction of RNA (2,3), suggests that thyroid hormone action may involve changes at the transcriptional level.…”

Section: Discussionmentioning

confidence: 99%

Triiodothyronine stimulates specifically growth hormone mRNA in rat pituitary tumor cells.

Seo¹,

Vassart²,

Brocas³

et al. 1977

Proc. Natl. Acad. Sci. U.S.A.

147

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In a cell-free protein-synthesizing system from a rabbit reticulocyte lysate, total RNA extracted from cultured rat pituitary tumor (GH3) cells directed, in a dose-related manner, the synthesis of proteins that were precipitated by antisera specific to rat growth hormone (somatotropin) and rat prolactin. A marked decrease in growth hormone secretion and growth hormone mRNA activity was observed when cells were grown in a medium deficient in thyroid hormone. Addition of triiodothyronine in physiologic amounts both prevented and completely reversed this effect within 48 hr. Thyroid hormone had no effect on prolactin secretion or prolactin mRNA activity. These data suggest that thyroid hormone may stimulate synthesis of growth hormone throug induction of transcriptional activity. The possibility of an additional effect at the posttranscriptional level has not been excluded. Although thyroid hormone is believed to have a general effect on a variety of metabolic processes, some effects, at the molecular level, may be quite selective, as indicated by the observed changes in growth hormone but not prolactin mRNA activity. The GH3 cell model is useful in the study of triiodothyronine action because of independence from secondary hormonal effects caused by hypothyroidism and because simultaneous measurement of prolactin mRNA activity serves as a unique internal control. The demonstration of triiodothyronine (T3) binding to nuclear proteins raises the possibility that thyroid hormone may regulate gene expression. Earlier work from Tata's laboratory showed that thyroid hormone-induced protein synthesis was preceded by formation of new RNA (1). Later, DeGroot et al. and Dilman et al. showed increase in the poly(A)-rich fraction of RNA (2, 3). Demonstrations of stimulation of a specific mRNA by thyroid hormones were recently provided by Kurtz et al. (4) and by Roy et al. (5) for a2u-globulin in the rat. However, because a number of hormones are known to stimulate the synthesis of this protein (6) and because thyroid hormone profoundly alters the level of such hormones (7), experiments done in the whole animal do not provide sufficient evidence for the direct induction of -d2u-globulin mRNA by thyroid hormone. Samuels et al. have reported a quantitative correlation between nuclear T3 receptor occupancy and stimulation of growth hormone (GH, somatotropin) synthesis in cultured rat pituitary cells (8). We have adopted a similar experimental model to study more directly the action of thyroid hormone on the induction of a specific mRNA. In a recent report, we have shown that GH and prolactin mRNA activities in the total RNA extracted from a rat pituitary cell line (GH3) that actively synthesizes both hormones can be quantitated using a rabbit reticulocyte lysate cell-free system (9). In this report, we show that in the normal rat serum were 5.4 ,ug/100 ml and 60 ng/100 ml, respectively, and in the Tx rat serum were 0.6 ,g/100 ml and less than 20 ng/100 ml, respectively. RNA Extraction. Each RNA preparation was obta...

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Section: Discussionmentioning

confidence: 99%

Triiodothyronine stimulates specifically growth hormone mRNA in rat pituitary tumor cells.

Seo¹,

Vassart²,

Brocas³

et al. 1977

Proc. Natl. Acad. Sci. U.S.A.

147

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“…These differences are consistent with adaptations for rapid development of foraging abilities necessary for the earlier nutritional independence in the former and extended periods of fasting during prolonged maternal dependence in the latter. The mechanisms controlling the physiological differences observed between the two species are unknown but are likely to involve thyroid hormones, which are known to play an important role in regulating metabolism and development in neonatal mammals (Bernal and Refetoff, 1977). While thyroid hormones have been shown to vary throughout development, lactation and between seasons in phocid seals (Haulena et al, 1998;John et al, 1987;Little, 1991;Litz et al, 2001;Woldstad and Jenssen, 1999), their dynamics in otariid seals remain to be investigated.…”

Section: Milk Consumption and Growth Strategymentioning

confidence: 99%

The comparative energetics and growth strategies of sympatric Antarctic and subantarctic fur seal pups at Îles Crozet

Arnould

Luque

Guinet

et al. 2003

Journal of Experimental Biology

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SUMMARY The period of maternal dependence is a time during which mammalian infants must optimise both their growth and the development of behavioural skills in order to successfully meet the demands of independent living. The rate and duration of maternal provisioning, post-weaning food availability and climatic conditions are all factors likely to influence the growth strategies of infants. While numerous studies have documented differences in growth strategies at high taxonomic levels, few have investigated those of closely related species inhabiting similar environments. The present study examined the body composition, metabolism and indices of physiological development in pups of Antarctic fur seals (Arctocephalus gazella) and subantarctic fur seals (Arctocephalus tropicalis), congeneric species with different weaning ages (4 months and 10 months, respectively), during their overlap in lactation at a sympatric breeding site in the Iles Crozet. Body lipid reserves in pre-moult pups were significantly greater(t28=2.73, P<0.01) in subantarctic (26%) than Antarctic fur seals (22%). Antarctic fur seal pups, however, had significantly higher (t26=3.82, P<0.001) in-air resting metabolic rates (RMR; 17.1±0.6 ml O2 kg-1min-1) than subantarctic fur seal pups (14.1±0.5 ml O2 kg-1 min-1). While in-water standard metabolic rate (SMR; 22.9±2.5 ml O2 kg-1min-1) was greater than in-air RMR for Antarctic fur seal pups(t9=2.59, P<0.03), there were no significant differences between in-air RMR and in-water SMR for subantarctic fur seal pups(t12=0.82, P>0.4), although this is unlikely to reflect a greater ability for pre-moult pups of the latter species to thermoregulate in water. Pup daily energy expenditure was also significantly greater (t27=2.36, P<0.03) in Antarctic fur seals (638±33 kJ kg-1 day-1) than in subantarctic fur seals (533±33 kJ kg-1 day-1), which corroborates observations that pups of the former species spend considerably more time actively learning to swim and dive. Consistent with this observation is the finding that blood oxygen storage capacity was significantly greater(t9=2.81, P<0.03) in Antarctic (11.5%) than subantarctic fur seal (8.9%) pups. These results suggest that, compared with subantarctic fur seals, Antarctic fur seal pups adopt a strategy of faster lean growth and physiological development, coupled with greater amounts of metabolically expensive behavioural activity, in order to acquire the necessary foraging skills in time for their younger weaning age.

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“…Deiodination resulting in a decreased concentration of plasma T 4 at days I and 5 may well account for the rise in T 3 at the same time periods without any increase in thyroid activity. Indeed such an augmented peripheral deiodination of T 4 to T 3 has been observed in leucocytes during the stress of infection (Bernal and Refetoff 1977). At days 10 and 20, however, the increased plasma concentration of T 3 was accompanied by an unchanged T 4 concentration.…”

Section: Resultsmentioning

confidence: 70%

“…During stress catecholamine secretion is greatly increased (Mason 1968). This increased concentration of catecholamines increases peripheral turnover of thyroid hormone (Bernal and Refetoff 1977) which may mask the full extent of the T 3 and T 4 changes owing to their decreased half-life.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Fertility of Frozen-Thawed Boar Semen

Maxweli¹,

Salamon²

1979

Aust. Jnl. Of Bio. Sci.

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Exposure of male CSF rats to a signalled unpredictable 60-day stress regimen induced a significant elevation in circulating triiodothyronine (T 3) concentration above the control for the first 20 days of stress before the rate of secretion returned to normal. On the other hand, circulating thyroxine (T 4) concentration fell significantly below the control value for the first 5 days of stress before the normal rate of secretion was reached by 10 days. A histological study of the thyroid gland revealed no change in activity among any of the control and stressed groups. At the same time this regimen also induced an initial extreme corticosterone elevation which was maintained for the first 5 days of stress and thereafter gradually fell to re-establish a new level by 40 days with no further change up to 60 days of stress.The possible physiological significance of the marked elevation in T 3/T 4 ratio as a result of stress is discussed, in particular with relation to higher glucocorticoid secretion.

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The Action of Thyroid Hormone

Cited by 104 publications

References 126 publications

Triiodothyronine stimulates specifically growth hormone mRNA in rat pituitary tumor cells.

Triiodothyronine stimulates specifically growth hormone mRNA in rat pituitary tumor cells.

The comparative energetics and growth strategies of sympatric Antarctic and subantarctic fur seal pups at Îles Crozet

Fertility of Frozen-Thawed Boar Semen

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