Structural characteristics of renomedullary interstitial cells of hypertensive ISIAH rats.

The structural characteristics of the renal medulla and its interstitial cells were studied in hypertensive ISIAH rats (in comparison with normotensive WAG rats) in order to clear out the role of the renomedullary interstitial cells in the mechanisms of AP regulation. Morphometric electron microscopic analysis and immunohistochemical studies in ISIAH rats detected the initial signs of the renomedullary sclerosis. The renomedullary interstitial cells of ISIAH rats were characterized by higher numerical density and were larger in size, with a higher volumic share of their secretory granules. These structural features of the studied cells were regarded as signs of their more intense functional activity aimed at hypertension suppression.

Chromogranin location in the adrenal glands of ISIAH rats.

Comparative immunohistochemical and electron microscopic study of the adrenals from hypertensive ISIAH rats and normotensive WAG rats (control) showed a more intense reaction to chromogranin A in the ISIAH adrenal in comparison with the control. Electron microscopy and morphometric analysis showed high volume and numerical densities of the secretory granules in chromaffin cells of hypertensive rats. The results indicate stimulation of the adrenal medullary substance in ISIAH rats. Presumably, intensive accumulation of chromogranin A and secretory granules in chromaffin cells of hypertensive rats reflects a certain imbalance of chromogranin A and catecholamines biogenesis, this, in turn, leading to stable stimulation of the sympathoadrenal component and higher stress sensitivity of these animals.

Cardiac natriuretic peptides and development of hereditary hypertension in rats.

Ultrastructure of the right atrial cardiomyocytes of suckling ISIAH rats was studied to clarify the role of cardiac natriuretic peptides in hypertension development during the period when blood pressure is not yet elevated. Cardiomyocytes diameter was significantly greater, Golgi complex was more developed, and granules in the sarcoplasm were more abundant in ISIAH rats as soon as on postnatal day 12 in comparison with age-matched normotensive animals. The smaller diameter of granules and their qualitative composition (ratio of forming, mature, and dissolving forms) attest to active synthesis and release of secretory product. In 21-day-old ISIAH rats, granule size and qualitative composition reflected increased accumulation of hormones in the cells. Thus, morphological features of increased production of natriuretic peptides in the right atrial myocytes were revealed in rats during the first postnatal month before manifestation of hereditary hypertension.

Structural characteristics of adenohypophysis in hypertensive ISIAH rats in early ontogeny.

Comparative morphological study of the adenohypophysis was conducted in 3-week-old normotensive WAG and hypertensive ISIAH rats (prehypertension period) to elucidate the role of the adenohypophysis in the development of essential hypertension. Morphometric analysis revealed ultrastructural signs of functional activation of somatotrophs, gonadotrophs, and corticotrophs in ISIAH rats. These peculiarities of structural organization of adenohypophysis in hypertensive rats can attest to enhanced response of the hypothalamic-pituitary-adrenal axis in these animals to natural stress associated with their transition to independent feeding. Increased stress sensitivity during the prehypertensive period of postnatal ontogeny contributes to the development of arterial hypertension.

Structural characteristics of renal glomerular system in ISIAH rats under conditions of chronic stress and preventive hypotensive drug therapy.

The effects of chronic stress on the structure and function of the renal glomerular system were studied in hypertensive ISIAH rats treated with hypotensive drugs during the early ontogeny. The morphometric parameters of the renal glomerular system, characteristic of each of the experimental animal groups treated by enalapril, losartan, or terazosin in early age virtually did not change under conditions of stress exposure. These results indicate a persistent delayed nephroprotective effect of these drugs.

Delayed effect of hypotensive drugs on blood pressure and structure of the myocardium in hypertensive ISIAH rats during chronic stress.

Administration of antihypertensive drugs alpha(1)-adrenoceptor antagonist and Ca(2+) channel blocker during early ontogeny had various delayed effects on blood pressure in ISIAH rats with inherited stress-induced arterial hypertension under resting conditions and chronic stress. The drugs did not prevent the development of myocardial hypertrophy. Chronic stress had little effect on myocardial structure in adult animals.

Structure of zona reticularis of adrenal cortex in hypertensive NISAG rats.

The structure of zona reticularis of the adrenal cortex in hypertensive NISAG rats was studied during the early, middle, and late periods of postnatal ontogeny. The detected morphological signs suggest that hypotrophic changes in zona reticularis of the adrenal cortex in hypertensive rats appeared before the onset of high blood pressure and accompanied the development of arterial hypertension in these animals.

[Morphometric characterization of hepatocytes during adaptation to extreme Antarctic factors].

The dynamics of ultrastructural changes in the hepatocytes of albino rats after prolonged influence of extreme Antarctic factors had been studied using the morphometric method. It was found that at the early stage of the experiment (7-45 days) the intracellular homeostasis in the hepatocytes was disturbed owing to a pronounced decrease in energy sources and plastic reserves (the decrease in numerical and volume density of the mitochondria, the reduction of the rough endoplasmic reticulum volume and the dilatation of its cisterns, the increase in the volume of the smooth endoplasmic reticulum). The following stages (up to 180 days) were characterized by a practically complete restoration of energy-plastic potential of the hepatocytes; at the conclusive stage of the experiment (270 days) the exhaustion of energy and, especially, of plastic reserves of the hepatocytes was noted (the significant decline in numerical density of the mitochondria and the relative volume of the rough endoplasmic reticulum).

[Cardiovascular peculiarities in hypertensive rats (Hsiah strain) after antihypertensive drug intervention during juvenile period of life].

Treatment with different types of antihypertensive drugs during second month age has not prevented development of arterial hypertension and myocardial hypertrophy in the adult rats with inherited stress-induced arterial hypertension. At 6 months of age, the 11% attenuation of basal blood pressure has beet achieved only in the rats treated with angiotensin-converting enzyme inhibitor enalapril. Nevertheless, they expressed the most pronounced left ventricular hypertrophy. The unfavorable tissue and ultrastructural abnormalities were revealed in the myocardium of the rats which received the alpha1-adrenoceptor blocker terazosin. The delayed effects of losartan (angionetsin II receptor antagonist) and corinfar (calcium channel antagonist) on the myocardial structure were inessential.

Delayed effects of hypotensive drugs on structural characteristics of the renal glomerular system in hypertensive NISAG rats.

Comparative morphometrical study of the renal glomerular system was carried out in hypertensive NISAG rats treated with hypotensive drugs during the prepubertal period. Blockade of the renin-angiotensin system with enalapril or losartan during the critical period of ontogeny (the 2nd month of life) produced a long-term hypotensive and renoprotective effect. Treatment with alpha-adrenoblocker terazosin during this period of ontogeny produced a less pronounced hypotensive effect, though with renoprotection. Corinfar (Ca2+ channel blocker) was least effective.

Delayed effects of enalapril on structural characteristics of the glomerular apparatus in the kidneys of NISAG rats.

Structural characteristics of renal glomeruli were studied in adult hypertensive NISAG rats (hereditary stress-induced hypertension) receiving antihypertensive drug enalapril, an inhibitor of angiotensin-converting enzyme, on days 28-58 of life. Treatment with enalapril (25 mg/kg perorally) in the early period of postnatal ontogeny produced delayed hypotensive and nephroprotective effects.

Age-related structural characteristics of the adrenal medulla in hypertensive NISAG rats.

Structural characteristics of the adrenal medulla in hypertensive NISAG rats (hereditary stress-induced arterial hypertension) were studied during various periods of postnatal ontogeny. Signs of hyperplasia of the adrenal medulla were most pronounced in adult hypertensive animals with persistent arterial hypertension, as well as during the period of late ontogeny.

[Stereomorphometric study of target organs in rats with hereditary stress-induced arterial hypertension at different periods of postnatal ontogenesis under changed conditions of nursing].

In rats with inherited stress-induced arterial hypertension (ISIAH strain), myocardium, adrenal gland, and renal glomerular apparatus were studied at different periods of postnatal ontogenesis (3 weeks and 6 months) to assess the influence of the changed conditions of nursing on the development of a hypertensive status and structural-functional characteristics of target organs. It was demonstrated that nursing of rats by foster normotensive Wistar females exerted a modulating influence upon the realization of stress-determined program of arterial hypertension development, seemingly delaying it and alleviating the negative consequences in respect to the target organs, through increased effectiveness of recruitment of adaptive-compensatory organism reserves, however, on the whole, it did not interrupt this program.

Structural characteristics of cardiomyocytes in the right atrium of NISAG rats.

Electron microscopy and stereomorphometric analysis of hypertrophic cardiomyocytes in the right atrium of NISAG rats revealed signs of activation of biosynthetic processes: increased relative volume of euchromatin (compared to Wistar rats), high density of nuclear pores, presence of large numerous Golgi complexes, and well-developed endoplasmic reticulum. The numerical density of secretory granules in the cytoplasm of cardiomyocytes in NISAG rats significantly surpassed that in Wistar rats. However, these granules in NISAG rats were smaller than in Wistar rats. The presence of numerous secretory granules and increased ratio of forming and dissolving structures suggest that this pool is characterized by high turnover rate, i.e., intensive synthesis and rapid elimination (consumption) of natriuretic peptide. Hypertrophy and hyperactivity of endocrine function in atrial cardiomyocytes of NISAG rats can be considered as a compensatory reaction to hypertension.

Effect of chronic stress during neonatal ontogeny on structural organization of the adrenal gland in hypertensive NISAG rats.

Structural organization of the adrenal gland was studied in 3-week- and 6-month-old hypertensive NISAG rats subjected to daily handling (10-min separation from mothers) on postnatal days 1-21. Neonatal handling reduces the stress-induced blood pressure rise in adult NISAG rats and modulates the structure of the adrenal cortex and medulla.

Effect of chronic stress during early postnatal ontogeny on structural characteristics of the myocardium and glomerular apparatus of the kidneys in NISAG rats.

We studied structural characteristics of the myocardium and glomerular apparatus of the kidneys in 3-week- and 6-month-old male NISAG rats (hereditary stress-induced arterial hypertension) subjected to handling on days 1-21 of postnatal ontogeny. The animals were daily isolated from mothers for 10 min. Handling did not modulate the development of arterial hypertension and typical morphological signs in the myocardium and kidneys.

Pathophysiological aspects of experimental myocardial infarction during arterial hypertension.

We compared the results of clinical and experimental studies of endocrine parameters in patients with myocardial infarction and arterial hypertension and NISAG rats with hereditary stress-induced arterial hypertension during experimental myocardial infarction. Changes in the content of corticosterone, aldosterone, insulin, triiodothyronine, and thyroxin were similar in animals and patients with myocardial infarction and arterial hypertension. The disadaptive course of myocardial infarction against the background of arterial hypertension can be explained by reduced compensatory capacity of the myocardium.

[Structure of the adrenal gland in rat strain with hereditary stress-induced arterial hypertension nursed by Wistar dams]. / Strukturnye osobennosti nadpochechnika krys linii s nasledstvennoi indutsirovannoi stressom arterial'noi gipertenziei pri vskarmlivanii samkami linii Wistar.

The comparative investigation of the adrenal structure in two groups of rats of Inherited Stress-Induced Arterial Hypertension (ISIAH) strain was conducted. The animals of the first group were nursed by normotensive Wistar rats, while those of the second (control) group were reared by their own mothers. The volume of the adrenal medulla in rats of the first group was found to exceed that in the second group. In the adrenal zona glomerulosa and zona fasciculata of 3-week-old rats of the first group parenchymal-stromal ratio and the average volume of adrenocorticocytes were lower than those in the animals of the second group. This was accompanied by a decrease in mitochondrial volume density and accumulation of lipid droplets in the cytoplasm, indicating a reduction of hormone-producing activity of endocrinocytes in the animals the first group as compared to controls. By 6 month of age, arterial pressure and quantitative parameters of adrenal medulla and cortex in the animals the first group were..... as compared to those in the second group. It is suggested that the nursing of ISIAH rat pups by normotensive Wistar dams had modulating effect on the adrenal structure and therefore on arterial hypertension development.

Peculiarities of myocardial structure in rats with hereditary hypertension reared by normotensive females.

Morphometric analysis revealed no signs of myocardial hypertrophy at the tissue and ultrastructural levels in 3-week-old NISAG rat pups reared by normotensive Wistar females. The severity of myocardial hypertrophy in these animals aging 6 months was similar to that in NISAG rats reared by natural mothers. However, raising conditions during the early ontogeny form compensatory structural changes in the myocardium of rats with genetically determined hypertension.

Structure of renal glomeruli in hypertensive NISAG rats reared by normotensive females.

Morphometry of ultrastructural components of renal glomeruli in 3-week- and 6-month-old rats with hereditary stress-induced arterial hypertension (NISAG rats) reared by normotensive Wistar females showed deceleration of the development of arterial hypertension in NISAG rats and attenuated its negative consequences for kidneys as the target organs.