The developmental switch in ventricular myosin expression in vivo is not triggered by an increase in cyclic AMP

1995 ◽  
Vol 7 (5) ◽  
pp. 1361 ◽  
Author(s):  
F Schachat ◽  
FJ Seidler ◽  
TA Slotkin
Keyword(s):  
Thyroid Hormone ◽  
Cyclic Amp ◽  
Acute Treatment ◽  
Time Course ◽  
Developmental Change ◽  
Relative Rate ◽  
Rapid Change ◽  
Pulse Labelling ◽  
Ventricular Myosin

Ventricular myosin heavy chain (HC) expression undergoes a rapid change from the beta to the alpha isoform shortly after birth. Thyroid hormone is required for this transition to occur, but the time course of developmental changes in circulating thyroid hormone levels suggests that it cannot be the trigger for this event. In this study, the possibility was examined that cyclic AMP (cAMP), either acting separately or as a mediator of the permissive actions of thyroid hormone, triggers the developmental transition in ventricular myosin HC expression. One-day-old euthyroid or propylthiouracil-hypothyroid rat pups were treated with a membrane-permeable cAMP analogue, 8-bromo-cAMP (8-Br-cAMP) or triiodothyronine (T3). Two and four hours after acute treatment, the relative synthetic rates of alpha and beta myosin HC were measured using an in vivo pulse labelling technique. Myosin HC isoforms were separated electrophoretically and then quantitated by densitometry. Acute treatment in vivo with 8-Br-cAMP did not alter the relative rate of alpha myosin HC synthesis in euthyroid animals at either 2 or 4 h. Hypothyroidism significantly reduced the relative rate of alpha HC synthesis and obturated the transition from beta to alpha HC. The effect on synthesis was rapidly reversed by acute treatment with T3, but not with 8-Br-cAMP. Thus, an increase in cAMP does not appear to trigger the developmental change in myosin isoform expression, nor does it appear to mediate the stimulatory effect of thyroid hormone on alpha myosin HC synthesis. Instead, thyroid hormone is likely to be acting directly on the alpha HC gene by binding to the thyroid response element. The identity of stimuli that mediate the increased responsiveness to thyroid hormone during development remains to be determined, but it is not due to an increase in the levels of cAMP in perinatal cardiocytes in vivo.

scholarly journals Measurement of the dynamics of stimulation and inhibition of steroidogenesis in isolated rat adrenal cells by using column perfusion

1974 ◽  
Vol 142 (2) ◽  
pp. 287-294 ◽  
Author(s):  
P. J. Lowry ◽  
Colin McMartin
Keyword(s):  
Cyclic Amp ◽  
Time Course ◽  
Acth Stimulation ◽  
Duration Of Action ◽  
Adrenal Cells ◽  
Small Column ◽  
Long Duration ◽  
Full Effect ◽  
Rapid Fall

Isolated adrenal cells were perfused in a small column by using Bio-Gel polyacrylamide beads as an inert supporting matrix, and the time-course of the response to various stimuli was observed by measuring fluorogenic 11-hydroxycorticosteroids in the effluent. A small but significant response was observed 1 min after stimulation with physiological concentrations of ACTH (adrenocorticotrophin), but the response did not start to build up rapidly for 3–4min and eventually reached a plateau after 9–10min. A similar pattern of events was observed for the decay of the steroid output on removal of ACTH. ACTH analogues, including one with a long duration of action in vivo, were found to produce responses with similar kinetics. However, cyclic AMP caused a more rapid increase in steroidogenesis and its effects were more short-lived after withdrawal. If, as present evidence suggests, cyclic AMP is produced rapidly after ACTH stimulation the delayed build-up of the steroidogenic response to ACTH would indicate that cyclic AMP may not be the intracellular mediator. When inhibitors were applied during ACTH stimulation, aminoglutethimide, which blocks mitochondrial conversion of cholesterol into pregnenolone (3β-hydroxypregn-5-en-20-one), caused a rapid fall in steroid output (1 min), whereas cycloheximide took longer to achieve its full effect. Nevertheless, the response had fallen by 50% in 2 min, indicating a much shorter half-life than that previously reported for the labile protein implicated in steroidogenesis. In addition the rapid response to cyclic AMP makes it unlikely that steroid production is induced as a result of initiation of protein synthesis. This suggests that the labile protein plays an obligatory but permissive role in the development of the response. Column perfusion has proved to be a simple technique which can readily yield accurate data on responses of cells to stimulants and inhibitors.

Time course of changes in albumin synthesis and mRNA in diabetic and insulin-treated diabetic rats

1985 ◽  
Vol 248 (6) ◽  
pp. E656-E663 ◽  
Author(s):  
D. E. Peavy ◽  
J. M. Taylor ◽  
L. S. Jefferson
Keyword(s):  
Total Protein ◽  
Time Course ◽  
Insulin Treatment ◽  
Relative Rate ◽  
Cdna Probe ◽  
Diabetic Rats ◽  
Rate Of Change ◽  
Albumin Synthesis ◽  
Albumin Mrna

Albumin synthesis in rat liver in vivo decreased from 12.7 to 2.2% of total protein synthesis during the first 3 days after the induction of diabetes and then remained relatively constant at this depressed rate for another 3 days. Insulin treatment begun on the 3rd day after the induction of diabetes restored albumin synthesis to control values within 3 days. Hybridization of total polyadenylate-containing RNA with a specific albumin cDNA probe revealed a close correspondence between the relative abundance of albumin mRNA and the relative rate of albumin synthesis after induction of diabetes and in response to insulin treatment. The apparent half-life of albumin mRNA, based on the rate of change of the message from one steady-state level to another, was approximately 22 h in both diabetic and insulin-treated diabetic rats. Diabetes of 3-day duration had no effect on the average sizes of total and albumin-synthesizing polysomes or on the ribosomal half-transit time for total protein and albumin. However, the number of albumin-synthesizing polysomes decreased as a result of diabetes to approximately one-third the number found in control livers. Taken together the results indicate that albumin synthesis was regulated by the availability of albumin mRNA and not by alterations in degradation, sequestration, or translation of message.

scholarly journals Stimulation by 6-N,2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate and glucocorticoids of phosphoenolpyruvate carboxykinase in the isolated perfused rat liver (Short Communication)

1974 ◽  
Vol 142 (3) ◽  
pp. 691-693 ◽  
Author(s):  
Wieland B. Huttner ◽  
Wilhelm Krone ◽  
Hans J. Seitz ◽  
Wolfgang Tarnowski
Keyword(s):  
Cyclic Amp ◽  
Cyclic Nucleotide ◽  
Time Course ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Direct Action ◽  
Isolated Perfused Rat Liver ◽  
Dibutyryl Cyclic Amp ◽  
Low Protein ◽  
Additive Increase

Dibutyryl cyclic AMP stimulated the activity of phosphoenolpyruvate carboxykinase in perfused livers of rats, fed on a low-protein diet, linearly over a 6h period. The enzyme activity was also significantly elevated by dexamethasone, the effect being considerably lower than that of the cyclic nucleotide. Since the time-course of phosphoenolpyruvate carboxykinase activity in response to dibutyryl cyclic AMP resembled that observed after dibutyryl cyclic AMP injection into intact animals, it is suggested that induction of the enzyme in vivo is due to a direct action of the cyclic nucleotide on the liver. Combined administration of dibutyryl cyclic AMP and glucocorticoids did not lead to an additive increase of liver phosphoenolpyruvate carboxykinase activity, either in vivo or in the perfused organ.

scholarly journals Adrenergic control of induction of type II iodothyronine 5′-deiodinase activity in cultured mouse brown adipocytes

1993 ◽  
Vol 292 (1) ◽  
pp. 303-308 ◽  
Author(s):  
S Pavelka ◽  
J Hermanská ◽  
M Baudysová ◽  
J Houstĕk
Keyword(s):  
Cyclic Amp ◽  
Time Course ◽  
Brown Fat ◽  
Fat Cells ◽  
Type Ii ◽  
Brown Adipocytes ◽  
Adrenergic Agents ◽  
Adrenergic Control ◽  
Stimulation Of

Iodothyronine 5′-deiodinase (5′D) of mouse brown adipocytes differentiated in cell culture was characterized in detail with respect to the adrenergic control of its biosynthesis. The stimulation of 5′D required mRNA and protein synthesis and was dependent on the stage of differentiation of the cells. The maximum induction was observed around confluence (7-day-old cells), in pre- and post-confluent cells the 5′D activity was significantly less induced. The transient responsiveness of brown fat-cells to the stimulatory effect of adrenergic agents was reflected also in the time course of the induction of 5′D by different concentrations of agonists. The maximum response occurred regularly after an 8 h incubation and implicated a rather fast turnover of the induced enzyme. On the basis of the inhibitory effects of cycloheximide and actinomycin D, the half-life of the induced 5′D and its mRNA were estimated to be 1.5 and 3.3 h respectively. The noradrenaline-induced 5′D activity was shown to be that of the type II enzyme, insensitive to propylthiouracil (PTU). The estimated values of its apparent Km for thyroxine, Km for the co-substrate dithiothreitol, and Vmax. in the presence of 1 mM PTU were 2 nM, 2.6 mM, and 0.1 pmol of I-/h per mg of protein respectively. The 5′D activity was effectively induced by forskolin and dibutyryl cyclic AMP, as well as by isoprenaline, noradrenaline and CGP-12177, but not by phenylephrine, cirazoline or oxymetazoline. This indicates that, contrary to previous observations in vivo, stimulation of 5′D in cultured brown fat-cells involves elevated cyclic AMP levels and is mediated predominantly via beta-receptors, particularly via the so-called beta 3-adrenoceptors.

scholarly journals Sensory Neuron Sodium Current Requires Nongenomic Actions of Thyroid Hormone During Development

2008 ◽  
Vol 100 (5) ◽  
pp. 2719-2725 ◽  
Author(s):  
Marc A. Yonkers ◽  
Angeles B. Ribera
Keyword(s):  
Thyroid Hormone ◽  
Time Course ◽  
Sodium Current ◽  
Active Form ◽  
Hormone Regulation ◽  
Zebrafish Model ◽  
Sodium Conductance ◽  
Rapid Effect ◽  
Touch Response

Development of the embryonic nervous system requires thyroid hormone. However, the underlying mechanisms and targets of thyroid hormone action are not well defined. To identify embryonic roles for thyroid hormone we tested for effects on a key neuronal trait, voltage-gated sodium current ( INa), in the zebrafish model system. We recorded from Rohon–Beard sensory neurons (RBs) using whole cell voltage-clamp methods. Here, we provide in vivo evidence for thyroid hormone regulation of INa. Chronic thyroid hormone application increased RB peak INa density 1.4-fold. However, INa density showed a similar increase within 5 min of an acute hormone application, a time course not expected for a genomic mechanism. Tetraiodothyroacetic acid (tetrac), a thyroid hormone blocker, blocked both chronic and acute effects. Further, the thyroid hormone precursor thyroxine (T4) affected INa, yet the traditionally active form triiodothyronine did not. Consequently, we tested for a nonconventional T4 receptor. LM609, a selective antagonist of integrin αVβ3, occluded the rapid effect of T4, implicating a specific integrin dimer as a T4 receptor. Chronic application of either tetrac or LM609 significantly reduced sodium conductance, demonstrating an in vivo requirement for T4-integrin regulation of INa. Further, removing endogenous T4 levels via yolkectomy reduced sodium conductance, an effect that was partially rescued by T4 supplementation following surgery. Because RBs mediate the embryonic touch response, we tested for behavioral effects. Tetrac and LM609 significantly reduced the percentage of touch trials eliciting a normal touch response. T4's rapid effect on RB INa highlights the importance of embryonic T4 availability and nongenomic T4 signaling.

The effect of triiodothyronine on cyclic AMP, phosphorylase, and adenyl cyclase in rat heart

1969 ◽  
Vol 47 (11) ◽  
pp. 913-916 ◽  
Author(s):  
John H. McNeill ◽  
Lawrence D. Muschek ◽  
Theodore M. Brody
Keyword(s):  
Thyroid Hormone ◽  
Cyclic Amp ◽  
Rat Heart ◽  
Adenyl Cyclase

Pretreatment with triiodothyronine (T3) greatly enhanced the epinephrine-induced increase in rat cardiac phosphorylase a. T3 treatment, however, did not increase the level of adenosine-3′,5′-monophosphate (cyclic AMP) in rat heart. T3 treatment also did not increase the activity of rat heart adenyl cyclase or change the sensitivity of the enzyme to epinephrine when activity was determined in vitro. It is suggested that if thyroid hormone affects the activity of adenyl cyclase in vivo the effect is lost in the preparation of the enzyme for assay in vitro.

DIFFERENCES IN ACTION OF LH AND FSH ON THE FORMATION OF CYCLIC AMP IN THE PREPUBERTAL RAT OVARY

1976 ◽  
Vol 81 (1) ◽  
pp. 150-164 ◽  
Author(s):  
Gunnar Selstam ◽  
Sten Rosberg ◽  
Jan Liljekvist ◽  
Lena Grönquist ◽  
Torsten Perklev ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Incubation Medium ◽  
Time Course ◽  
Tissue Levels ◽  
Rat Ovary ◽  
Camp System ◽  
High Concentrations ◽  
Camp Levels

ABSTRACT The actions of LH (NIH-LH-B8) and FSH (NIH-FSH-S9) on the cyclic AMP (cAMP) system in ovaries of 23–24 day old rats have been analyzed. An intravenous injection of LH increased ovarian cAMP levels in vivo after only 20 seconds. Maximal cAMP levels were seen after 15 min. Addition of LH or FSH in vitro to the isolated ovaries produced dose dependent increases of cAMP in the tissue as well as in the incubation medium. Low concentrations of LH caused a release of cAMP into the incubation medium without any detectable change in the tissue levels. The levels of cAMP in the incubation media for all concentrations of FSH were lower than the tissue levels, whereas for LH the opposite was found. In time-course experiments where the concentrations of LH (10 μg/ml) and FSH (100 μg/ml) were chosen to give similar tissue levels of cAMP, the release of the cyclic nucleotide into the incubation medium was approximately 2–3 times greater for LH than for FSH at the time periods studied (5–240 min). When LH and FSH were tested together in high concentrations, their effects were additive. When the ovaries were first incubated with FSH for 120 min followed by an incubation with LH, the stimulatory effect of LH was considerably reduced. When the order of the incubations was reversed, however, LH did not change the response to FSH. The results show that both LH and FSH have intrinsic effects on the cAMP system in the prepubertal rat ovary, but that the effects of the two gonadotrophins are not identical.

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