Carcinoid: the cause

The cause of carcinoid development, as well as other tumors, is still unclear. It was noted that many symptoms of the disease are due to hormonal activity of the tumor. With the greatest degree of certainty, significant isolation by cells of a tumor of serotonin (5-hydroxytryptamine), the product of the conversion of the amino acid tryptophan, has been demonstrated, and in the blood its content reaches 0.1-0.3 μg / ml. Under the influence of monoamine oxidase, the bulk of serotonin is converted to 5-hydroxyindolylacetic acid, excreted in the urine. In the urine, the content of the final product of its conversion - 5-hydroxyindolylacetic acid (5-GOIUK) - is sharply increased in carcinoid and in most cases is 50-500 mg (at a rate of 2-10 mg).

The formation of serotonin from tryptophan is a complex enzymatic process that takes place in several phases. The biological functions of serotonin, as is known, are unusually wide. He is involved in the regulation of the central nervous system, has vasoconstrictor properties, increases the tone of smooth muscles, blood coagulation, regulates blood supply to the kidneys, etc. In humans, the injection of serotonin causes an increase in arterial pressure in the bradycardia, marked bronchospasm with asthmatic attacks, almost universal smooth muscle spasm , pain and tenesmus of the intestines and bladder, in women - contractions of the uterus). The motility of the digestive tract increases, the secretion of all digestive juices, including saliva. In the body, serotonin is mainly in bound form; most of it is fixed in platelets. Associated forms of serotonin are physiologically inert. In the binding of serotonin, some proteins, lipids, cellular polysaccharides participate.

The physiological activity of sertonin is manifested when it is in the blood in a free state. The release of serotonin by the tumor accounts for the complex complex of the body's reactions observed during carcinoid (serotonin) attacks.

In recent years, it has been proved that the tumor produces other biologically active substances: lysyl-bradykinin and bradykinin, formed as a result of the action of kallikreins on kininogens (related to plasma a2-globulins), histamine, prostaglandins and, as shown in recent decades, and the polypeptide P , i.e., is multi-hormonal.

The arthentaffin cells from which the carcinoid is formed are also referred to in the literature as enterochromaffine, basal granular (in the basal part of the cells there are granules that, when histochemically studied, they give argentaffine, chromaffin, acidic, alkaline and other reactions), yellow cells, intragenous arthamentinocytes Kulchitsky), Heidenhain, Schmidt.

It was found that these cells are not only diffusely scattered in the mucosa of the digestive tract, but also occur in other organs and perform an endocrine function. Initially, it was suggested to call the system of these cells "diffuse endocrine organ" or "diffuse endocrine system", and since 1954 the term "paracrine glands" has been used. Later Pearse (1968-1972) developed the concept of "APUD-system", which includes the system of endocrine cells and has the ability to absorb the amine precursors followed by decarboxylation and isolation of amines - oligopeptides (histamine, serotonin, choline, etc.), as well as polypeptide hormones . There are about 15 types of these intestinal argeta-affinocytes (there are probably more of them) and their classification is suggested.

The study of endocrine cells of the gastrointestinal tract is of great importance, in particular, for a better understanding of the essence of carcinoid tumors and an explanation of the clinical features of these diseases. Differences in endocrine ("general") symptoms of carcinoid tumors in patients are explained by a wide range of biologically active substances produced by the cells of these tumors.

A typical clinical picture of carcinoid syndrome is most typical for tumors originating from the jejunum and the cecum.

[1], [2], [3]