The Author’s Commentary on the Article “Distinctive Features of Criticality in the Operation of Membrane Na + /K + -ATPases” [1]

The appearance of this commentary on the recently published article “Distinctive features of criticality in the work of membrane Na+/K+-ATPases” in the journal Acta Scientific Clinical Case Reports, (2021), 2(8): 84-90 [1] is explained by the authors’ desire to discuss the correctness of using hair spectrometry for assessment of elemental homeostasis in the human body in toto. It is for this purpose that the mentioned methodological approach continues to be applied in many medical centers.

important role in the generation of membrane potential and in other reactions of cellular metabolism.
It is no coincidence that there is a powerful, well-coordinated regulatory system that works on the principle of feedback to ensure the optimal content of Na and K in the body. It includes endocrine (hypothalamus, pituitary, adrenal cortex) and other organs (kidneys, lungs, intestines, skin), well-known hormones: vasopressin, aldosterone, myocardial natriuretic hormone, etc., as well as vascular baroreceptors and hypothalamic osmoreceptors.
Not all details of this homeostatic control are fully understood, but its rather high level is undoubted, as one can judge by the relatively small fluctuations in the normal content of Na and K in plasma (Na: 135 -152 mmol/l; K: 3.6 -6, 3 mmol/l) and in urine (Na: up to 340 mmol/day; K: 39 -91 mmol/day). And although the given indicators are not adequate to the total amount of these metals in the organism (in toto), they convincingly demonstrate the effectiveness of homeostatic regulation in relation to Na and K in the most important biological media.
It is significant that we failed to find such a control in the epidermis and its derivative (hair). The content of Na and K in hair (median), which was measured using atomic emission spectrometry in 10297 apparently healthy residents of Moscow and Riga aged from 2 to 85 years (5160 men and 5137 women without any symptoms of diselementosis), varied widely: sodium -from 0.645 µg/g to 9240 µg/g; potassium -from 0.045 µg/g to 6505.1 µg/g [2].
Such a scatter of spectrometric data can be explained (at least presumably) by the presence of two unrelated systems of Na/K homeostasis: at the organismal and cellular (epidermis and its derivatives) level. And since the measured parameters in each of the autonomously working homeostatic systems should be considered within the framework of only the system in which they were obtained, the extrapolation of the hair spectrometry data to the whole organism cannot be considered justified.
The very possibility of participation of a complex multilevel system providing in toto homeostasis of Na and K (and, possibly, other metals) in the MLH control of constantly (and rather rapidly) renewing epidermis with its derivatives looks unrealistic.
Experience has shown that the "differences" (by several orders of magnitude!) in the values of the concentration of Na and K in the hair of the subjects did not in any way affect their well-being and/ or objective status. Along with it, any lethal risks are completely excluded, unlike in toto situations, where such risks are very relevant with much smaller changes in sodium and/or potassium concentrations in plasma.
At the same time, the use of the main provisions of the theory of self-organized criticality (SC) and spectrometric analysis helps to explain some key events in the MLH of the epidermis. We are talking about the emerging opportunity (according to hair spectrometry data) to reliably diagnose the critical and subcritical phases in the operation of the main membrane pumps for the transport of metals in the epidermis -ATPases from the P-type family (and first of all, The identification of these phases from the results of spectrometry is available when constructing in a logarithmic scale of Pareto plots, reflecting the probability density of the power-law distribution (PDF). In this case, the critical state is characterized by Here it is necessary to make an explanation that was not included in the text of the mentioned article but seems important to warn the reader of possible inaccuracy in the author's interpretation of the data obtained. The fact is that to find the С thr point in our work we used the results of atomic emission spectrometry of hair for the content of Na and K obtained from 10,000 healthy individuals (5,000 men and 5,000 women) at the age of 20-45 years. But as a criterion for the distribution of subjects into two categories (with subcritical and critical modes of operation of membrane Na + /K + -ATPases), the found C thr point on the Pareto graphs for Na and K was used in individuals of different ages: from 2 to 86 years (947 healthy individuals and 954 liquidators of the Chernobyl accident).
The age discrepancy between the studied groups can, apparently, affect the results of measuring each of the phases although it is unlikely to significantly affect the conclusions of the authors.

Conclusion
In conclusion, I would like to offer clinicians some recommendations on the use of metal spectrometry in such a biosubstrate as hair. It is hoped that the proposed recommendations will be in demand, since the capabilities and advantages of the spectrometric analysis itself are becoming more and more popular in the clinic.

B. In addition, the value of measured indicators is closely related
to the sex and age of the subjects. In some metals (for example, Ca, Mg, V, etc.), hair spectrometry revealed significant sex differences in normal values (the "female norm" for Ca may exceed the "male" one by more than two times). The age factor plays an equally important role for the correct interpretation of spectrometric analysis. According to our data, there are significant age-related differences in the content of Na and K in hair. Normal values (median) of these metals (bootstrapmethod) in healthy people aged 2 to 9 years: Na -324.9 μg/g; K -376.9 μg/g; age 20-49 years: Na -99.9 μg/g; K -47.1 μg/g; age 60-85 years: Na -293.9 μg/g; K -121.4 μg/g [2]. A possible relationship with age (preliminary data) was also found in other metals (Ca, Al, Cd, Cr, Cu, Fe, Li, Pb, V, Zn). Therefore, a reliable assessment of the results of spectrometry should include mandatory consideration of gender and age.