High activity of semicarbazide-sensitive amine oxidase (SSAO): an important source of errors in the determination of the concentration of dopamine in pig plasma

The Biological Implication of Semicarbazide-Sensitive Amine Oxidase (SSAO) Upregulation in Rat Systemic Inflammatory Response under Simulated Aerospace Environment

The progress of space science and technology has ushered in a new era for humanity's exploration of outer space. Recent studies have indicated that the aerospace special environment including microgravity and space radiation poses a significant risk to the health of astronauts, which involves multiple pathophysiological effects on the human body as well on tissues and organs. It has been an important research topic to study the molecular mechanism of body damage and further explore countermeasures against the physiological and pathological changes caused by the space environment. In this study, we used the rat model to study the biological effects of the tissue damage and related molecular pathway under either simulated microgravity or heavy ion radiation or combined stimulation. Our study disclosed that ureaplasma-sensitive amino oxidase (SSAO) upregulation is closely related to the systematic inflammatory response (IL-6, TNF-α) in rats under a simulated aerospace environment. In particular, the space environment leads to significant changes in the level of inflammatory genes in heart tissues, thus altering the expression and activity of SSAO and causing inflammatory responses. The detailed molecular mechanisms have been further validated in the genetic engineering cell line model. Overall, this work clearly shows the biological implication of SSAO upregulation in microgravity and radiation-mediated inflammatory response, providing a scientific basis or potential target for further in-depth investigation of the pathological damage and protection strategy under a space environment.

The oxidation of dopamine and epinine by the two forms of monoamine oxidase from rat liver

Information on the "in vitro" oxidation of epinine by monoamine oxidase (MAO) compared to dopamine is very poor. The aim of this work was to study the oxidative deamination of epinine and dopamine by rat liver MAO-A and MAO-B. The contributions of MAO-A and B to the metabolism of dopamine (55% and 45%, respectively) and epinine (70% and 30%, respectively) were similar. The results of this study show that epinine is a substrate for both forms of MAO in rat liver, although the contribution of MAO A to the deamination of this secondary amine appears to be slightly more important than that of MAO B.

Breakdown of 3,4-dihydroxybenzylamine and dopamine in plasma of various animal species by semicarbazide-sensitive amine oxidase

We report a rapid breakdown of dopamine and especially of 3,4-dihydroxybenzylamine, the frequently-used internal standard in catecholamine determinations, in plasma of many but not all animal species. Species investigated were cow, sheep, goat, pig, horse, rabbit, dog, guinea pig, mouse, chicken, rat and man. In some species 3,4-dihydroxybenzylamine nearly completely disappeared at 4 degrees C within 15 min after addition to the plasma. Added dopamine, but not norepinephrine and epinephrine, also rapidly disappeared at 4 degrees C. Disappearance rates were increased at higher temperatures, and at 20 degrees C also norepinephrine showed some breakdown. The breakdown is caused by a semicarbazide-sensitive amine oxidase in the plasma, and can be completely blocked by the addition of the inhibitor semicarbazide. Measurement of plasma catecholamine concentrations in animal species can thus lead to erroneous results, especially when 3,4-dihydroxybenzylamine is used as an internal standard. Only when blood is collected in tubes containing an inhibitor of semicarbazide-sensitive amine oxidase like semicarbazide can reliable plasma catecholamine measurements be performed.