RADIATION DAMAGE OF SERUM IN THE PRESENCE OF PROTECTIVE AGENTS BY THERMAL NEUTRONS AND X RAYS

Journal Article · Thu Jan 01 04:00:00 EST 1959 · Acta Pharmacologica et Toxicologica (Denmark)

DOI:https://doi.org/10.1111/j.1600-0773.1959.tb01175.x· OSTI ID:4120981

Hendrickx, A

>As an approach to understanding the mechanism underlying radioprotection by sulfhydryl agents, serum levels of sulfhydryl (-SH) and disulfide (-S-S-) groups were measured, and their reaction to thermal neutrons and gamma rays in the presence of a protective agent, such as cysteine, cystine, cysteinamine, and cystamine was studied. It was shown that serum contains reactive -S-S- groups, and that the reactivity of -SH and -S-S- varies with the age of the serum donor. Cystine and serum behave differently under the influence of radiation; cystine is destroyed, whereas serum shows an increase in titrable -SH and -S-S- groups. The serum in a 5-ml Pyrex vessel was irradiated for various periods with a 1 g Ra-Be source. In an air-free aqueous solution cysteine is resistant to radiation; an initial concentration of 12.46 mg -SH/100 ml decreased only to a value of 11.61 mg after 120-minutes irradiation. Cysteinamine with an initial value of 14.64 decreased to 3.63 mg -SH/100 ml; thus it decomposes much more rapidly than cysteine. With cystine, 3.02 mg -SH/100 ml appeared after 120 min. Here -SH groups appeared which were not found before irradiation. The same phenomenon occurred in experiments with cystamine. The cysteine reaction in the presence of serum showed the presence of fewer -SH groups even when there was no irradiation. Cysteinamine and serum reacted in a similar way to cysteine and serum. On irradiating cysteine solutions, no -S-S- groups could be detected after various periods of irradiation up to 120 min. This indicates that under the experimental conditions used, cysteine is not oxidized in presence of neutrons or gamma rays. Cysteinamine behaved similarly. On adding cysteine to serum the initial value of 4.80 mg -S-S-/100 ml rose to 7.40 mg -S-S-/100 ml after 120-minutes irradiation, With cysteinamine and serum the initial value of 1.44 mg -S-S-/ 100 ml was increased to 6.70 mg -S-S-/100 ml after 120 minutes irradiation. On irradiating serum the amount of -S-S- increased from 4.65 mg/100 mi to 6.24 mg/100 ml after 120 minutes. On adding cystine, cystamine, or cysteamine to serum the amount of -S-S- groups that could be detected without any irradiation was lowered. This can be explained by complex formation. Thus it was shown that on adding the radioprotective agents cystine, cysteine, or cystamine to serum, a precipitate formed before irradiation had taken place. After centrifugation and analysis of the -SH and -S-S- content in the supernatant fluid the original amounts of -SH and -S-S- were found. It was therefore concluded that all titratable -SH and -S-S- groups are absent from the precipitate. In the experiments with aerated solutions an increased amount of -S-S- was noted when serum was irradiated in the presence of cysteine or cystamine. The reaction scheme is therefore more complicated than was thought by some radiobiologists. It cannot be restricted simply to peroxide or free radical formation. Complex formation and steric structural relations of the protein, play a more important part. The effect of thermal neutrons and gamma rays on the behavior of -SH and -S-Sgroups in albumin differs from that on the whole serum. (BBB)

• Research Organization: Rijksuniversiteit, Ghent
• Sponsoring Organization: USDOE
• NSA Number: NSA-18-011850
• OSTI ID: 4120981
• Journal Information: Acta Pharmacologica et Toxicologica (Denmark), Journal Name: Acta Pharmacologica et Toxicologica (Denmark) Vol. Vol: 15; ISSN APTOA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

AGE
BERYLLIUM
BIOLOGY AND MEDICINE
BLOOD SERUM
CENTRIFUGATION
COMPLEXES
CYSTAMINE
CYSTEINE
CYSTINE
FREE RADICALS
GAMMA RADIATION
MEASURED VALUES
ORGANIC SULFUR COMPOUNDS
OXIDATION
PRECIPITATION
QUALITATIVE ANALYSIS
QUANTITY RATIO
RADIATION INJURIES
RADIATION PROTECTION
RADIATION SOURCES
RADIOSENSITIVITY
RADIUM
SOLUTIONS
THERMAL NEUTRONS
WATER