Aldosterone and stress-dependent arterial hypertension

Animal Models of Hypertension (ISIAH Rats), Catatonia (GC Rats), and Audiogenic Epilepsy (PM Rats) Developed by Breeding

Research into genetic and physiological mechanisms of widespread disorders such as arterial hypertension as well as neuropsychiatric and other human diseases is urgently needed in academic and practical medicine and in the field of biology. Nevertheless, such studies have many limitations and pose difficulties that can be overcome by using animal models. To date, for the purposes of creating animal models of human pathologies, several approaches have been used: pharmacological/chemical intervention; surgical procedures; genetic technologies for creating transgenic animals, knockouts, or knockdowns; and breeding. Although some of these approaches are good for certain research aims, they have many drawbacks, the greatest being a strong perturbation (in a biological system) that, along with the expected effect, exerts side effects in the study. Therefore, for investigating the pathogenesis of a disease, models obtained using genetic selection for a target trait are of high value as this approach allows for the creation of a model with a "natural" manifestation of the pathology. In this review, three rat models are described: ISIAH rats (arterial hypertension), GC rats (catatonia), and PM rats (audiogenic epilepsy), which are developed by breeding in the Laboratory of Evolutionary Genetics at the Institute of Cytology and Genetics (the Siberian Branch of the Russian Academy of Sciences).

Comparative studies on endogenic stress hormones, antioxidant, biochemical and hematological status of metabolic disturbance in albino rat exposed to roundup herbicide and its active ingredient glyphosate

There have been growing concerns and uncertainty about reports attributing the metabolic disturbance induced by a commercial formulation of glyphosate-based herbicide to its active ingredient. We therefore compared the effects of Roundup Original® and its active ingredient glyphosate on some hypothalamic-pituitary-adrenal (HPA) hormones and oxidative stress markers, biochemical and hematological profiles in 56 adult male albino rats randomly assigned to seven treatments of eight rats per treatment. The rats were orally exposed to Roundup Original® and its active ingredient daily at 3.6 mg/kg body weight (bw), 50.4 and 248.4 mg/kgbw of glyphosate equivalent concentrations for 12 weeks, while control treatment received distilled water. Serum concentrations of corticosterone, adrenocorticotropic hormone, aldosterone and concentration of oxidative stress marker, biochemical and hematological profiles in the blood were determined. Concentrations of corticosterone and aldosterone were significantly higher (p < 0.05) in rats treated with Roundup in a dose-dependent manner. Reduced glutathione concentration, catalase, and butyrylcholinesterase activities reduced significantly in rats treated with Roundup relative to those treated with the active ingredient. Lipid peroxidation was observed in rats treated with Roundup. Biochemical and hematological profiles of rats treated with Roundup were significantly altered (p < 0.05). However, significant changes in only acid phosphatase, lactase dehydrogenase, bilirubin, and white blood cells in rats treated with the active ingredient at 50.4 mg/kg were observed. The severe metabolic disturbance and stress observed in rats treated with the commercial formulation of Roundup herbicide may not be associated with the mild changes induced by the active ingredient.

Effects of hypoestrogenism and/or hyperaldosteronism on myocardial remodeling in female mice

We investigated the potential adverse effects of hyperaldosteronism and/or hypoestrogenism on cardiac phenotype, and examined their combined effects in female mice overexpressing cardiac aldosterone synthase (AS). We focused on some signaling cascades challenging defensive responses to adapt and/or to survive in the face of double deleterious stresses, such as Ca2+ -homeostasis, pro/anti-hypertrophic, endoplasmic reticulum stress (ER stress), pro- or anti-apoptotic effectors, and MAP kinase activation, and redox signaling. These protein expressions were assessed by immunoblotting at 9 weeks after surgery. Female wild type (FWT) and FAS mice were fed with phytoestrogen-free diet; underwent ovariectomy (Ovx) or sham-operation (Sham). Ovx increased gain weight and hypertrophy index. Transthoracic echocardiograghy was performed. Both Ovx-induced heart rate decrease and fractional shortening increase were associated with collagen type III shift. Cardiac estrogen receptor (ERα, ERβ) protein expression levels were downregulated in Ovx mice. Hypoestrogenism increased plasma aldosterone and MR protein expression in FAS mice. Both aldosterone and Ovx played as mirror effects on up and downstream signaling effectors of calcium/redox homeostasis, apoptosis, such as concomitant CaMKII activation and calcineurin down-regulation, MAP kinase inhibition (ERK1/2, p38 MAPK) and Akt activation. The ratio Bcl2/Bax is in favor to promote cell survivor. Finally, myocardium had dynamically orchestrated multiple signaling cascades to restore tolerance to hostile environment thereby contributing to a better maintenance of Ca2+ /redox homeostasis. Ovx-induced collagen type III isoform shift and its upregulation may be important for the biomechanical transduction of the heart and the recovery of cardiac function in FAS mice. OVX antagonized aldosterone signaling pathways.

Neonatal reflexes and behavior in hypertensive rats of ISIAH strain

Hypertension is one of the most common diseases in humans, and there is a special concern on the consequences of maternal hypertensive conditions for the health of newborns. An inherited stress-induced arterial hypertension (ISIAH) rat strain has been selected but only a few studies have addressed behavior in these rats. Body weight, neurodevelopmental reflexes, and neuronal density in the hippocampus were compared in ISIAH and normotensive WAG rats during their suckling period. Systolic and diastolic blood pressure (SBP, DBP), adult rat performance in the open field (OF), elevated plus maze (EPM), and novel object recognition (NOR) tests were evaluated at the age of 12-14weeks old. Body weight in pups did not differ significantly during the suckling period, while adult ISIAH rats were heavier than age-matched WAG rats and possessed the increased SBP and DBP. ISIAH pups were developmentally more advanced than WAG as indicated by grasp reflex and negative geotaxis reaction scores. This was associated with higher neuronal density in CA1 and CA3 hippocampal areas in ISIAH pups on postnatal day 6 as compared to WAG rats. Adult ISIAH rats demonstrated an increased locomotor and exploratory activity in the OF and EPM tests as well as low levels of anxiety. The NOR test revealed no significant difference in recognition but confirmed higher exploratory activity in ISIAH rats compared to WAG rats. The results indicate that hypertensive ISIAH rats feature accelerated development during their suckling period, and as adults, they are more active and less anxious than normotensive WAG rats.

Parameters of Blood Flow in Great Arteries in Hypertensive ISIAH Rats with Stress-Dependent Arterial Hypertension

Magnetic resonance angiography was used to examine blood flow in great arteries of hypertensive ISIAH and normotensive Wistar rats. In hypertensive ISIAH rats, increased vascular resistance in the basin of the abdominal aorta and renal arteries as well as reduced fraction of total renal blood flow were found. In contrast, blood flow through both carotid arteries in ISIAH rats was enhanced, which in suggests more intensive blood supply to brain regulatory centers providing enhanced stress reactivity of these rats characterized by stress-dependent arterial hypertension.