scholarly journals The effect of iodothyronines on the conversion of thyroxine into 3,3′-5-tri-iodothyronine in isolated rat renal tubules

1980 ◽  
Vol 190 (2) ◽  
pp. 239-242
Author(s):  
P Heyma ◽  
R G Larkins ◽  
D G Campbell
Keyword(s):  
Dose Response ◽  
Intact Cell ◽  
Cell System ◽  
Renal Tubules ◽  
Reverse T3 ◽  
Naturally Occurring ◽  
Collagenase Digestion ◽  
Isolated Rat

Isolated rat renal tubules prepared by collagenase digestion were used to study the effects of 3,3′,5′-tri-iodothyronine (‘reverse T3’, rT3) and other iodothyronines on the formation of 3,3′,5-tri-iodothyronine (T3) from thyroxine (T4). rT3 inhibited the conversion with a dose response over the concentration range 1.5nM-1.5microM. The inhibition was competitive in nature. Both 3,3′-di-iodothyronine and 3′,5′-di-iodothyronine also inhibited the production of T3 and T4 in isolated rat renal tubules, but tetraiodothyroacetic acid and 3,5-di-iodothyronine were found to have no effect. These experiments demonstrate in an intact cell system that some naturally occurring iodothyronines have significant effects on T4 deiodination.

Glucocorticoids Decrease the Conversion of Thyroxine into 3,5,3′-Tri-Iodothyronine by Isolated Rat Renal Tubules

1982 ◽  
Vol 62 (2) ◽  
pp. 215-220 ◽  
Author(s):  
P. Heyma ◽  
R. G. Larkins
Keyword(s):  
Strong Evidence ◽  
Glucocorticoid Receptors ◽  
Actinomycin D ◽  
Time Dependent ◽  
Renal Tubules ◽  
Short Term ◽  
Collagenase Digestion ◽  
Isolated Rat

1. The effect of glucocorticoids on the deiodination of thyroxine (T4) to 3,5,3′-tri-iodothyronine (T3) was studied in rat renal tubules prepared by collagenase digestion. 2. In short-term (6 h) experiments, cortisol and dexamethasone inhibited the conversion of T4 into T3 at concentrations of 2 × 10-4 mol/l and 2 × 10-5 mol/l respectively. The inhibition by cortisol and dexamethasone was time dependent and was prevented by actinomycin D and progesterone, suggesting that the inhibition is mediated by an effect on nuclear transcription dependent on binding to glucocorticoid receptors. 3. In long-term (16 h) experiments, cortisol and dexamethasone inhibited T4 to T3 conversion by the tubules at concentrations of 1 × 10-12 mol/l and above. In addition, physiological concentrations of corticosterone (1 × 10-8 mol/l) were able to decrease T3 generation from T4. 4. Our data provide strong evidence that physiological concentrations of glucocorticoids are able to affect T3 production from T4 directly and suggest that they may be important regulators of T4 deiodination.

The Formation of Tri-Iodothyronine and Reverse Triiodothyronine from Thyroxine in Isolated Rat Renal Tubules

1978 ◽  
Vol 55 (6) ◽  
pp. 567-572
Author(s):  
P. Heyma ◽  
R. G. Larkins ◽  
J. R. Stockigt ◽  
D. G. Campbell
Keyword(s):  
Therapeutic Range ◽  
Inhibitory Effect ◽  
Renal Tubules ◽  
Intact Cells ◽  
Reverse Triiodothyronine ◽  
Collagenase Digestion ◽  
Subsequent Degradation ◽  
Isolated Rat

1. Conversion of thyroxine into triiodothyronine and reverse tri-iodothyronine in intact cells was studied with isolated renal tubules prepared by collagenase digestion. 2. Conversion of thyroxine into triiodothyronine and reverse tri-iodothyronine increased progressively for at least 90 min. 3. Studies of tri-iodothyronine production from increasing amounts of thyroxine revealed that the thyroxine to tri-iodothyronine conversion is saturable. 4. Iodide and carbimazole had no effect on the thyroxine to tri-iodothyronine conversion. 5. 6-Propyl-2-thiouracil had a direct noncompetitive inhibitory effect on the conversion of thyroxine into tri-iodothyronine with a 75% inhibition of the conversion at a propylthiouracil concentration within the therapeutic range in vivo. Propylthiouracil also inhibited the net formation of reverse tri-iodothyronine from thyroxine at a similar propylthiouracil concentration, as well as inhibiting the subsequent degradation of reverse triiodothyronine.

The Renal Aminoacidurias

1963 ◽  
Vol 9 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Harold A Harper ◽  
Paul D Doolan
Keyword(s):  
Amino Acids ◽  
Glomerular Filtration ◽  
Maximum Rate ◽  
Renal Tubule ◽  
Renal Tubules ◽  
Naturally Occurring ◽  
Clinical Interest ◽  
The Individual ◽  
Filtered Load ◽  
Metabolic Significance

Abstract The normal mechanisms whereby the renal tubules handle amino acids are reviewed as a basis for interpretation of the physiologic causes of the renal aminoacidurias. Under normal circumstances, the renal tubules reabsorb in excess of 93% of the amino acids filtered from the plasma. When the filtered load of amino acids is increased, as by intravenous injection of amino acids, there is an increase in both the amounts reabsorbed and those excreted, but the ability of the renal tubule to respond to an increased filtered load of amino acids is so great that a maximum rate of reabsorption has not been found in the human. However, the tubule does exhibit selectivity with respect to the reabsorption of each of the naturally occurring L-amino acids; furthermore, there is a much greater efficiency of reabsorption of the L as compared to the D isomers of the individual amino acids. The excretion of amino acids is influenced to an important degree by the glomerular filtration rate, as exemplified by studies in pregnant subjects as well as patients with renal disease affecting glomerular filtration. Several renal aminoacidurias of clinical interest are discussed with special reference to their diagnostic and metabolic significance.

scholarly journals Natriuretic and antikaliuretic effects of uroguanylin and prouroguanylin in the rat

2010 ◽  
Vol 299 (6) ◽  
pp. F1433-F1442 ◽  
Author(s):  
Nicholas G. Moss ◽  
Dorothy A. Riguera ◽  
Robert C. Fellner ◽  
Christopher Cazzolla ◽  
Michael F. Goy
Keyword(s):  
Dose Response ◽  
Sodium Excretion ◽  
Enterochromaffin Cells ◽  
Active Principle ◽  
Renal Tubules ◽  
Low Doses ◽  
Peptide Fragment ◽  
Response Curves ◽  
Renal Sodium Excretion ◽  
Intravenous Infusions

The peptide uroguanylin (Ugn) is stored and released as a propeptide (proUgn) by enterochromaffin cells in the intestine, and converted to Ugn and other metabolites in the renal tubules. Both proUgn and Ugn are natriuretic, although the response to proUgn is thought to depend on its conversion to Ugn within nephrons. To assess the efficiency of intrarenal conversion of proUgn to Ugn, we measured urinary Ugn excretion in rats following intravenous infusions of proUgn or Ugn. Infusion of 2 and 10 nmol proUgn/kg body wt increased plasma proUgn concentration from 2.2 ± 0.3 to 5.6 ± 1.3 pmol/ml and to 37 ± 9.6 pmol/ml, respectively. No proUgn was detected in urine before, during, or after proUgn infusions. These two proUgn infusion doses resulted in total Ugn recovery in urine of 162 ± 64 and 206 ± 39 pmol/kg body wt (9 and 2% of the infused amount, respectively). By contrast, the same molar amounts of Ugn resulted in 1,009 ± 477 and 5,352 ± 2,133 pmol/kg body wt of Ugn in urine (recoveries of ∼50%). Unexpectedly, comparisons of natriuretic dose-response curves for each peptide showed proUgn to be about five times more potent than Ugn, despite the relatively modest amount of Ugn generated from infused proUgn. In addition, both peptides were antikaliuretic at low doses, but in this case Ugn showed greater potency than proUgn. These data do not support Ugn as the primary active principle of proUgn for regulation of renal sodium excretion. Instead, an alternative peptide fragment produced from proUgn may be responsible for natriuretic activity in the kidney, whereas Ugn itself may play an antikaliuretic role.

Naturally occurring opioid peptides modulate H+-production by isolated rat parietal cells

Peptides ◽  
1986 ◽  
Vol 7 (5) ◽  
pp. 885-890 ◽  
Author(s):  
W. Schepp ◽  
J. Schneider ◽  
V. Schusdziarra ◽  
M. Classen
Keyword(s):  
Opioid Peptides ◽  
Parietal Cells ◽  
Naturally Occurring ◽  
Isolated Rat

Isolation and characterization of goat ovarian aromatase cDNA: assessment of the activity using an intact cell system and placental expression

2004 ◽  
Vol 62 (3-4) ◽  
pp. 532-543 ◽  
Author(s):  
Raúl José Bobes ◽  
Carolina Miranda ◽  
Mario Pérez-Martinez ◽  
Van Luu-The ◽  
Marta C Romano
Keyword(s):  
Intact Cell ◽  
Cell System ◽  
Isolation And Characterization

scholarly journals The translocation, folding, assembly and redox-dependent degradation of secretory and membrane proteins in semi-permeabilized mammalian cells

1995 ◽  
Vol 307 (3) ◽  
pp. 679-687 ◽  
Author(s):  
R Wilson ◽  
A J Allen ◽  
J Oliver ◽  
J L Brookman ◽  
S High ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Intact Cell ◽  
Cell System ◽  
In Vitro Translation ◽  
Tissue Type ◽  
Translation System ◽  
Secretory Proteins ◽  
Permeabilized Cell ◽  
Permeabilized Cells

We describe here a semi-permeabilized cell-system which reconstitutes the efficient synthesis, translocation, folding, assembly and degradation of membrane and secretory proteins. Cells grown in culture were treated with the detergent digitonin which selectively permeabilized the plasma membrane leaving the cellular organelles, such as the endoplasmic reticulum (ER) and trans-Golgi network intact. These permeabilized cells were added to an in vitro translation system, either wheatgerm or reticulocyte lysate, supplemented with RNA coding for either membrane or secretory proteins. Efficient translocation and modification of proteins by these cells was demonstrated by protease protection, photocross-linking of nascent chains to components of the translocation apparatus and by post-translational modifications such as glycosylation or hydroxylation. A comparison was made between the ability of semi-permeabilized cells and microsomal vesicles to fold and assemble proteins. The results show that the intact ER within these cells can assemble proteins much more efficiently than vesicularized ER. Furthermore, the semi-permeabilized cells carried out the redox-dependent degradation of tissue-type plasminogen activator. This system has all the advantages of conventional cell-free systems, including speed and, importantly, the ability to manipulate the components of the assay, while retaining intracellular organelles and, therefore, allowing cellular processes to occur as they would in the intact cell.

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