Comparative Analysis of the State of Intrarenal and Intradermal Microcirculation and Excretory Kidney Function in Carbofos Poisoning

The dissertation is devoted to a comparative analysis of the state of intrarenal and intradermal microcirculation, as well as excretory kidney function, in carbofos poisoning — a phosphorus-organic pesticide widely used in agriculture and household activities. The study is conducted on animal models using the method of laser Doppler flowmetry to assess microhemodynamics in the skin and the cortical substance of the kidneys. Both routes of poisoning — oral and dermal — in the LD20 dose are considered, with analysis of microcirculation indicators, functional state of the kidneys, and morphometric parameters of nephrons at various observation time points.

The work is aimed at identifying features of the state of the peripheral circulation system in the skin and microcirculation of the cortical substance of the kidneys under the influence of small doses of carbofos, as well as at assessing the interrelationship between changes in skin microcirculation and the functional state of the kidneys. The scientific novelty consists in the first-time conducted comparative study of microhemodynamics of renal cortex and skin after different routes of carbofos poisoning, which makes it possible to substantiate the use of laser Doppler flowmetry as an auxiliary means for early diagnosis of the degree of organ damage in poisoning by phosphorus-organic compounds.

The relevance of the problem. One of the urgent problems of modern medicine remains the study of the toxic effect on the organism of phosphorus-organic pesticides, including carbofos, used in household and agricultural activities [12, 73, 109]. It has been noted that phosphorus-organic compounds are applied to approximately 4 billion hectares of land worldwide [100], therefore they are widely distributed in the external environment [12, 73, 146]. It has been calculated that pesticide poisoning of varying severity is detected annually in approximately 2 million people worldwide, with 50,000 cases resulting in a lethal outcome [107, 130].

In Western European countries, the number of patients with acute pesticide poisoning was approximately 2 per 1,000 inhabitants in the 1970s, whereas in the previous decade this indicator was 1 per 1,000 [172]. According to data from poisoning centers in our country, patients with acute poisoning by phosphorus-organic insecticides constitute 1.8–6.3% among all hospitalized patients. The significance of this pathology is determined by the severity of intoxication and high mortality. Thus, according to data by E.A. Luzhnikov, hospital mortality in such cases amounts to 20–24% [68]. In severe poisonings, even with the use of modern treatment methods (detoxification, complex antidotal and pathogenetic therapy), it may reach 30–50% and higher [68, 154].

In humans, poisoning by phosphorus-organic substances, and in particular carbofos, develops when these preparations enter the stomach, through the respiratory tract, and through the skin. Carbofos easily penetrates through the skin and biological membranes. Upon oral ingestion, absorption begins in the oral cavity and continues in the stomach and small intestine. Toxic substances quickly enter the bloodstream and are distributed in organs and tissues. In this process, higher concentrations are detected in the kidneys, liver, lungs, intestines, and central nervous system.

A number of authors draw attention to the increase in recent years in the number of cases of pesticide damage through the respiratory tract and the high mortality associated with developing pneumonias [1, 2, 11], although they are capable of causing disturbances in all vital organs: the central nervous system, kidneys, liver, gastrointestinal tract, cardiac muscle, and others [1, 2, 10, 11, 12, 10, 41, 59, 100, 158, 162].

Particular emphasis should be placed on the effect of phosphorus-organic pesticides on the functional state and morphological structure of the kidneys [3, 8, 15, 62, 64, 89, 90], damage to which may become a cause of death. It has been shown that disturbances of kidney function may manifest as oliguria or polyuria, nycturia, isosthenuria, decreased glomerular filtration and renal blood flow, and elevated blood urea levels. Morphological changes in kidney tissue manifest as damage to the renal epithelium, swelling of capillary endothelium in glomeruli, and sometimes tubulorrhexis.

The difficulty of determining the dose of phosphorus-organic compounds entering the organism and the challenges of assessing the degree of damage to internal organs in poisonings make the problem of searching for accessible markers for assessing the severity of damage urgent, which may contribute to more timely and successful execution of diagnostic measures and, ultimately, to the conduct of a more targeted therapeutic strategy and a favorable prognosis [189].

In connection with this, it should be noted that under the action of various doses of phosphorus-organic compounds, disturbances of peripheral circulation in various organs and tissues have been detected, including in the skin. The identified changes are characterized, for example, by swelling of the vascular endothelium and the appearance of lymphocytic infiltrates in the vessel wall [24, 57, 100]. This makes it potentially possible to judge about the damage to the organism by phosphorus-organic compounds through the study of features of microcirculation in the skin.

One of the modern methods for investigating the microcirculation system is the use of laser Doppler flowmetry. This method, on the one hand, meets the requirements of non-invasiveness and harmlessness of conducting studies in humans, and on the other hand, provides the opportunity to obtain objective information both about the state of tissue microhemodynamics and about violations of the mechanisms of its regulation [61, 196].

Taking into account the above, it seemed important to trace and compare in the experiment the degree of alteration of hemimicrocirculation indicators in the cortical substance of the kidneys and in the skin of animals, using the method of laser Doppler flowmetry, under the action of small doses of carbofos, alongside the assessment of the state of excretory kidney function.

The goal of the study was to conduct a comparative analysis of the state of the peripheral circulation system in the skin, in relation to the state of microcirculation, structural and functional state of the cortical substance of the kidneys, upon dermal and oral action of carbofos in the LD20 dose.

Tasks of the study

1. To study the features of microcirculation in the skin of rats after oral administration of carbofos in the LD20 dose.

2. To study indicators characterizing the functional activity of the kidneys in animals after oral administration of carbofos in the LD20 dose.

3. To study the features of microcirculation in the cortical substance of the kidneys in rats after dermal action of carbofos in the LD20 dose.

4. To study morphometric indicators of the state of nephrons of the kidneys in animals subjected to dermal action of carbofos in the LD20 dose.

5. Having compared the obtained results, to identify the main indicators of the state of skin microcirculation characterizing the severity of disorders resulting from carbofos poisoning in the LD20 dose.

Scientific novelty. For the first time, using the method of laser Doppler flowmetry, a comparative study of the state of microhemodynamics of the cortical substance of the kidneys after dermal carbofos poisoning (in the LD20 dose) and the state of microcirculation of the skin after oral administration of carbofos (in the same dose) was conducted.

It was first discovered that after oral administration of carbofos in the LD20 dose, a sharp depression of microcirculation in the skin occurs, which is due to a decrease in the intensity of both local, active mechanisms of microhemodynamics regulation and central, passive mechanisms of control. These disorders persisted throughout the entire study period (up to 15 days of observation). Characteristically, they were accompanied by persistent polyuria, proteinuria, and changes in a number of other indicators characterizing the functional activity of the kidneys.

It has been shown that after dermal application of carbofos in the LD20 dose, there is a depression of active mechanisms of regulation of renal microcirculation, a decrease in vasomotor activity of microvessels of the cortical substance of the kidneys, which is accompanied by a decrease in morphometric indicators of nephrons. It was found that structural changes in the kidneys persist for 12 hours after carbofos poisoning, while functional disorders of the microhemodynamics system of the cortical substance of the kidneys are detected within 48 hours of observation.

Scientific significance of the work. As a result of the work, the features of microcirculation in the cortical substance of the kidneys and in the skin, as well as their regulatory systems after carbofos poisoning in the LD20 dose, were identified. This allows for a new assessment of their interrelationship and also testifies to the rapid alteration of the microcirculation system in response to the action of phosphorus-organic compounds on the organism.

Practical significance of the work. The results obtained make it possible to recommend the method of laser Doppler flowmetry of the microcirculatory bed of the skin as an auxiliary method for early diagnosis and determination of the degree of damage to the organism in carbofos poisoning.

Propositions to be defended.

1. Dermal carbofos poisoning in the LD20 dose causes depression of the activity of the microcirculatory system of the cortical substance of the kidneys, a decrease in vasomotor activity of microvessels, which is accompanied by a decrease in morphometric indicators of nephrons.

2. Oral administration of carbofos in the LD20 dose causes a more rapid and permanent decrease in the level of indicators characterizing blood filling of microvessels in the skin, due to the suppression of active and passive mechanisms of their regulation. These changes were combined with a disturbance of a number of indicators of the functional state of the kidneys.

3. Assessment of the state of microcirculation in the skin by the method of laser Doppler flowmetry in cases of poisoning with small doses of phosphorus-organic compounds is a sufficiently informative method for characterizing the degree of impairment of kidney function and the organism as a whole.

4. The most significant fumometric parameters characterizing the disturbance of the state of microcirculation in the skin, which can be used for diagnostic purposes, are the microcirculation index, its root mean square deviation, and the amplitude indicators of active oscillations of microblood flow.

Implementation of the research results.

The results obtained in the course of the work are used at the Department of Forensic Medicine of SGMMA when analyzing materials related to the toxic action of small doses of carbofos on the organism, at the Department of Histology of SGMMA when studying the system of peripheral circulation of various organs and tissues, and at the Department of Pathophysiology.

Publications. Eleven works have been published on the topic of the dissertation.