Identification of Mineralocorticoid Receptors, Aldosterone, and Its Processing Enzyme CYP11B2 on Parasympathetic and Sympathetic Neurons in Rat Intracardiac Ganglia

Recent interest has focused on the mineralocorticoid receptor (MR) and its impact on the myocardium and the performance of the heart. However, there is a lack of evidence about MR expression and its endogenous ligand aldosterone synthesis with specific regard to the intrinsic cardiac nervous system. Therefore, we looked for evidence of MR and aldosterone in sympathetic and parasympathetic neurons of intracardiac ganglia. Tissue samples from rat heart atria were subjected to conventional reverse-transcriptase polymerase chain reaction (PCR), Western blot, and double immunofluorescence confocal analysis of MR, corticosterone-inactivating enzyme 11β-hydroxysteroid-dehydrogenase-2 (11β-HSD2), aldosterone, and its processing enzyme CYP11B2 together with the neuronal markers vesicular acetylcholine transporter (VAChT) and tyrosine hydroxylase (TH). Our results demonstrated MR, 11β-HSD2, and CYP11B2 specific mRNA and protein bands in rat heart atria. Double immunofluorescence labeling revealed coexpression of MR immunoreactivity with VAChT in large diameter parasympathetic principal neurons. In addition, MR immunoreactivity was identified in TH-immunoreactive small intensely fluorescent (SIF) cells and in nearby VAChT- and TH-immunoreactive nerve terminals. Interestingly, the aldosterone and its synthesizing enzyme CYP11B2 and 11β-HSD2 colocalized in MR– immunoreactive neurons of intracardiac ganglia. Overall, this study provides first evidence for the existence of not only local expression of MR, but also of 11β-HSD2 and aldosterone with its processing enzyme CYP11B2 in the neurons of the cardiac autonomic nervous system, suggesting a possible modulatory role of the mineralocorticoid system on the endogenous neuronal activity on heart performance.

Microscopic and submicroscopic structure of the heart atria and auricles in condition of the experimental thermal trauma

Burns is the damage of the skin or mucous membranes (often with underlying tissues), because of high-temperature influence (thermal burns), chemical, electrical, radiation, combined, thermochemical and electrothermal factors influence. According to the investigations, burns rank third among other injuries, and in some countries, second, second only to transport injuries. Although the level of survival after burns is increasing, the problem of their treatment remains relevant in modern medicine and pharmacy. The aim was to study the peculiarities and the patterns of morphofunctional changes in the structural components of the heart atria and auricles in case of the experimental thermal trauma. The study involves 30 adult guinea pigs with a bodyweight of 630-670 g. The burn was applied under general ether anesthesia with water vapor at a temperature of 96-97 0C on the surface of the skin of the animal's back for 60 seconds. The size of the lesion area was 18-20% of the body surface. The depth of the lesion corresponded to the degree ІІІА -IIIB. The experimental animals were divided into two groups: the first - intact guinea pigs (6 heads); second - animals with thermal trauma (24 heads). Were used a number of methods of investigation, including macrometric and massometric - to establish the structural restructuring of the heart and its parts, microscopic and electron microscopic to detect changes in the structural components of the atrium and auricle of the heart; morphometric - to obtain quantitative parameters of the morphological components of the heart; mathematical and statistical - to ensure the analysis of the reliability of the research results. In intact guinea pigs, the morphological organization of the heart auricles differs from the atria by the direction of the muscle fibers, the ratio of morphometric parameters of their structural components and the content of muscle endocrine cells. Submicroscopically, endocrine myocytes of the auricles of the heart contain more hormonal granules than atria. In the ears of the heart, the relative volume of connective tissue is 1,34 times greater, and the relative volume of muscle fibers is 1,03 times smaller than in the atria. Submicroscopically, endocrine muscle cells of the heart auricle contain more hormonal granules than atria. It has been established that thermal trauma causes significant morphofunctional changes in the atria and auricles of the heart at different levels of their structural organization. The degree of damage depends on the duration of the experiment and develops against the background of increased plasma toxicity. In the stages of burn shock and early toxemia, adaptive-compensatory processes develop in the structures of the heart, and irreversible destructive changes occur in the stages of late toxemia and septicotoxemia.