a1_Fifty years ago, Lewis K. Dahl has presented a new model of salt hypertension – salt-sensitive and salt-resistant Dahl rats. Twenty years later, John P. Rapp has published the first and so far the only comprehensive review on this rat model covering numerous aspects of pathophysiology and genetics of salt hypertension. When we summarized 25 years of our own research on Dahl/Rapp rats, we have realized the need to outline principal abnormalities of this model, to show their interactions at different levels of the organism and to highlight the ontogenetic aspects of salt hypertension development. Our attention was focused on some cellular aspects (cell membrane function, ion transport, cell calcium handling), intra- and extrarenal factors affecting renal function and/or renal injury, local and systemic effects of reninangiotensin-aldosterone system, endothelial and smooth muscle changes responsible for abnormal vascular contraction or relaxation, altered balance between various vasoconstrictor and vasodilator systems in blood pressure maintenance as well as on the central nervous and peripheral mechanisms involved in the regulation of circulatory homeostasis. We also searched for the age-dependent impact of environmental and pharmacological interventions, which modify the development of high blood pressure and/or organ damage, if they influence the saltsensitive organism in particular critical periods of development (developmental windows). Thus, severe self-sustaining salt hypertension in young Dahl rats is characterized by pronounced dysbalance between augmented sympathetic hyperactivity and relative nitric oxide deficiency, attenuated baroreflex as well as by a major increase of residual blood pressure indicating profound remodeling of resistance vessels. Salt hypertension development in young but not in adult Dahl rats can be attenuated by preventive increase of potassium or calcium intake., a2_On the contrary, moderate salt hypertension in adult Dahl rats is attenuated by superoxide scavenging or endothelin-A receptor blockade which do not affect salt hypertension development in young animals., J. Zicha, ... [et al.]., and Obsahuje seznam literatury
Hypertension is the risk factor of serious cardiovascular diseases, such as ischemic heart disease and atherosclerosis. The aim of the present study was to analyze the development of cardiac tolerance to ischemia in neonatal spontaneously hypertensive rats (SHR) and possible protective effect of ischemic preconditioning (IP) or adaptation to intermittent high-altitude hypoxia (IHAH). For this purpose we used 1- and 10-day-old pups of SHR and their normotensive control Wistar Kyoto rats (WKY). Isolated hearts were perfused in the Langendorff mode with Krebs-Henseleit solution at constant pressure, temperature and rate. Cardiac tolerance to ischemia was expressed as a percentage of baseline values of developed force (DF) after global ischemia. IP was induced by three 3-min periods of global ischemia, each separated by 5-min periods of reperfusion. IHAH was simulated in barochamber (8 h/day, 5000 m) from postnatal day 1 to 10. Cardiac tolerance to ischemia in 1-day-old SHR was higher than in WKY. In both strains tolerance decreased after birth, and the difference disappeared. The high cardiac resistance in 1- and 10-day-old SHR and WKY could not be further increased by both IP and adaptation to IHAH. It may be concluded that hearts from newborn SHR are more tolerant to ischemia/reperfusion injury as compared to age-matched WKY; cardiac resistance decreased in both strains during the first ten days, similarly as in Wistar rats., Z. Charvátová, ... [et al.]., and Obsahuje seznam literatury
Hypertension is one of the major risk factor of cardiovascular diseases, but after a century of clinical and basic research, the discrete etiology of this disease is still not fully understood. One reason is that blood pressure is a quantitative trait with multifactorial determination. Numerous genes, environmental factors as well as epigenetic factors should be considered. There is no doubt that although the full manifestation of hypertension and other cardiovascular diseases usually occurs predominantly in adulthood and/or senescence, the roots can be traced back to early ontogeny. The detailed knowledge of the ontogenetic changes occurring in the cardiovascular system of experimental animals during particular critical periods (developmental windows) could help to solve this problem in humans and might facilitate the age-specific prevention of human hypertension. We thus believe that this approach might contribute to the reduction of cardiovascular morbidity among susceptible individuals in the future., J. Kuneš, ... [et al.]., and Obsahuje seznam literatury
Impressive advances in molecular genetic techniques allow to analyze the effects of natural selection on the development of human genome. For example, the trend towards blonde hair and blue eyes was documented. The approach to analyze possible effects of natural selection on the evolution of recent phenotypes with high risk of cardiovascular disease has not been described yet. A possible effect on the evolution of two main risk factors - hypercholesterolemia and hypertension - is presented. The close relationship of non-HDL cholesterol blood concentration to the proportion of pro-inflammatory macrophages in human visceral adipose tissue might be a result of long-lasting natural selection. Individuals with higher proportion of this phenotype might also display a higher ability to fight infection, which was very common in human setting from prehistory until Middle Ages. Successful battle against infections increased the probability to survive till reproductive age. Similar hypothesis was proposed to explain frequent hypertension in African Americans. A long-lasting selection for higher ability to conserve sodium during long-term adaptation to low sodium intake and hot weather was followed by a short-term (but very hard) natural selection of individuals during transatlantic slave transport. Only those with very high capability to retain sodium were able to survive. Natural selection of phenotypes with high plasma cholesterol concentration and/or high blood pressure is recently potentiated by high-fat high-sodium diet and overnutrition. This hypothesis is also supported by the advantage of familial hypercholesterolemia in the 19th century (at the time of high infection disease mortality) in contrast to the disadvantage of familial hypercholesterolemia during the actual period of high cardiovascular disease mortality., R. Poledne, J. Zicha., and Seznam literatury
Blood pressure (BP) level results from the balance of vasoconstrictors (mainly sympathetic nervous system) and vasodilators (predominantly nitric oxide and endothelium-derived hyperpolarizing factor). Most of the forms of experimental hypertension are associated with sympathetic hyperactivity and endothelial dysfunction. It is evident that nitric oxide and norepinephrine are antagonists in the control of calcium influx through L-type voltage-dependent calcium channels (L-VDCC). Their effects on L-VDCC are mediated by cGMP and cAMP, respectively. Nevertheless, it remains to determine whether these cyclic nucleotides have direct effects on L-VDCC or they act through a modulation of calcium-activated K+ and Cl- channels which influence membrane potential. Rats with genetic or salt hypertension are characterized by a relative (but not absolute) NO deficiency compared to the absolute enhancement of sympathetic vasoconstriction. This dysbalance of vasoconstrictor and vasodilator systems in hypertensive animals is reflected by greater calcium influx through L-VDCC susceptible to the inhibition by nifedipine. However, when the modulatory influence of cyclic nucleotides is largely attenuated by simultaneous ganglionic blockade and NO synthase inhibition, BP of spontaneously hypertensive rats remains still elevated compared to normotensive rats due to augmented nifedipine-sensitive BP component. It remains to determine why calcium influx through L-VDCC of hypertensive rats is augmented even in the absence of modulatory influence of major vasoactive systems (sympathetic nervous system, nitric oxide)., M. Pintérová ... [et al.]., and Obsahuje seznam literatury
Chronic kidney disease (CKD) is a life-threatening disease arising as a frequent complication of diabetes, obesity and hypertension. Since it is typically undetected for long periods, it often progresses to end-stage renal disease. CKD is characterized by the development of progressive glomerulosclerosis, interstitial fibrosis and tubular atrophy along with a decreased glomerular filtration rate. This is associated with podocyte injury and a progressive rise in proteinuria. As endothelin-1 (ET-1) through the activation of endothelin receptor type A (ETA) promotes renal cell injury, inflammation, and fibrosis which finally lead to proteinuria, it is not surprising that ETA receptors antagonists have been proven to have beneficial renoprotective effects in both experimental and clinical studies in diabetic and non-diabetic CKD. Unfortunately, fluid retention encountered in large clinical trials in diabetic CKD led to the termination of these studies. Therefore, several advances, including the synthesis of new antagonists with enhanced pharmacological activity, the use of lower doses of ET antagonists, the addition of diuretics, plus simply searching for distinct pathological states to be treated, are promising targets for future experimental studies. In support of these approaches, our group demonstrated in adult subtotally nephrectomized Ren-2 transgenic rats that the addition of a diuretic on top of renin-angiotensin and ETA blockade led to a further decrease of proteinuria. This effect was independent of blood pressure which was normalized in all treated groups. Recent data in non-diabetic CKD, therefore, indicate a new potential for ETA antagonists, at least under certain pathological conditions., I. Vaněčková, S. Hojná, M. Kadlecová, Z. Vernerová, L. Kopkan, L. Červenka, J. Zicha., and Seznam literatury