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Determination of 3,5,3′-triiodo-L-thyronine (T3) levels in tissues of rainbow trout (Salmo gairdneri) and the effect of low ambient pH and aluminum (1990)

Fok, Pearl ; Eales, J. G. ; Brown, S. B.

Springer

Fish physiology and biochemistry 8 (1990), S. 281-290

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ISSN: 1573-5168

Keywords: triiodothyronine ; trout ; low pH ; Al ; tissue T3 extraction

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Tissue T3 (3,5,3′-triiodo-L-thyronine) concentrations were measured in rainbow trout, Salmo gairdneri, after digestion by Pronase or collagenase and extraction with ethanolic ammonia (99:1, v/v) followed by 2N NH4OH and chloroform. Recoveries of [125I]T3 administered in vivo or in vitro were high and consistent and there was close parallelism between sample dilutions and the radioimmunoassay curve, but recoveries of unlabeled T3 administered in vitro were low and variable. Alternatively, trout were brought to isotopic equilibrium by [125I]T3 infusion for 96 h, the extracted [125I]T3 determined by gel filtration and the tissue T3 content calculated from the specific activity of plasma [125I]T3. By the latter method, tissue T3 concentrations were: intestine (4.2 ng/g), kidney (2.5), liver (2.8), stomach (1.5), heart (1.0), muscle (0.7), gill (0.6) and skin (0.3). Muscle (67% of body weight) comprised the largest tissue T3 pool (82% of all tissues examined). Seven days exposure of trout to water acidified with H2SO4 (pH 4.8) or acidified water containing aluminum (21.6 mM), decreased tissue T3 content generally and particularly in muscle (14% of controls). In conclusion, skeletal muscle is the largest T3 tissue pool and seems highly responsive to altered physiologic state.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00003423

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Development of a sensitive peptidase assay: In search of cell associated proteases responsible for the cleavage of prepro TGFα (1992)

Brown, S. B. ; Krause, D. ; Townsend, E. ; [et al.]

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 48 (1992), S. 411-423

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ISSN: 0730-2312

Keywords: cognate peptide substrate ; preprotein processing ; prepro TGFα ; HeLa cells ; cell surface proteases ; aminopeptidases ; endopeptidases ; product profiling ; thin layer chromatography ; factor regulation ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: A radiometric assay has been developed for the detection of proteolytic activity capable of releasing transforming growth factor alpha (TGFα) from its membrane bound precursor. The assay is dependent upon the separation by thin layer chromatography of hydrolytic products of a nonapeptide substrate containing a radioactive iodinated tyrosine residue as a reporting group N-terminal to an octapeptide which is cognate to the N-terminal cleavage sequence of TGFα. We describe the selectivity of the peptidase assay with commercially purified proteases and with cell-associated peptidases, its exquisite sensitivity, and its applicability to defining peptidase activity, which may be responsible for the processing of the membrane-bound prepro TGFα. The activity of two different elastases had different profiles which thus may be of use in characterizing them. The characteristics of the intact and extracted HeLa cell assay with respect to time, cell density, and peptidase concentration are defined, as are conditions needed to remove endogenous, confounding, proteolytic activity from the serum used to support cell culture. Intact HeLa cell cultures exhibit both exo- and endo-peptidase activity at approximately equal levels in both sparse and dense monolayer culture without relationship to cell density, and at a level equal to 1-2% of total cell activity of these enzyme classes.

Additional Material: 6 Ill.