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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric nephrology 4 (1990), S. 421-423 
    ISSN: 1432-198X
    Keywords: Ontogeny ; Gene expression ; Renin-angiotensin system ; Renin release ; Angiotensin-converting enzyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Evidence for the expression of genes of the renin-angiotensin system (RAS) in the developing kidney is rapidly accumulating. We have recently demonstrated that the fetal kidney expresses the renin gene and that expression of the gene is developmentally regulated. Kidney renin messenger ribonucleic acid (mRNA) levels decrease markedly with maturation, and as maturation unfolds the intrarenal distribution of renin and its mRNA changes from large intrarenal arteries in the fetus to a restricted juxtaglomerular site in the adult animal. These findings demonstrate that renin is synthesized and stored in the aforementioned vascular segments and that expression of the renin gene follows the centrifugal pattern of nephrovascular development. In addition to storing renin, intact kidney microvessels release renin spontaneously and possess a functionally active adenylate cyclase whose stimulation results in a marked increase in renin release. The increase in renin enzymatic activity appears to be due to a recruitment of renin-releasing cells rather than to an increase in the amount of renin secreted per cell. Expression of the angiotensinogen (Ao) gene is also developmentally regulated. Ao mRNA levels are very low in the fetal liver, markedly increasing after parturition, suggesting that some of the complex neurohumoral changes surrounding extrauterine life may regulate the expression of the Ao gene. As in the adult animal, Ao is expressed in fetal kidney, brain and brown adipose tissue. The contribution of these organs to the fetal plasma pool of Ao remains to be determined. However, unlike the adult, the fetal liver may not be the primary source of circulating Ao in the fetus. The distribution of angiotensin-converting enzyme in the developing kidney differs from that of the adult kidney. In human fetuses, the enzyme is located in microvilli and basolateral membranes of proximal tubules, and at the cleft of S-shaped glomeruli and in glomerular capillaries of more mature nephrons. As maturation proceeds, localization in peritubular capillaries becomes manifest and glomerular localization becomes restricted to a few endothelial cells. This changing pattern of enzyme localization may be of importance in the regulation of glomerular and post-glomerular hemodynamics and tubular fluid reabsorption. In summary, the three genes of the RAS are expressed in the fetal kidney. The distribution of the encoding proteins follows a unique developmental pattern that may be important for the early establishment of a paracrine angiotensin(s) generating system.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-198X
    Keywords: Kidney ; Renin ; Innervation ; Ontogeny ; Double-label immunohistochemistry ; Sprague-Dawley rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The development of renin-containing cells and nerve fibers was studied in Sprague-Dawley rat kidneys during the last third of gestation and the first 15 days of postnatal life. Kidney tissue sections were stained for nerve fibers or double stained employing an anti-rat renin polyclonal antibody and a monoclonal antibody (TUJ1) directed against a neuron-specific class III beta-tubulin isotype. Renin-containing cells and nerve fibers were detected at 17 days of gestation, in close spatial relationship along the main branches of the renal artery. During fetal life, renin-containing cells and nerve fibers were spatially associated along arcuate and interlobular arteries, renincontaining cells being also present throughout the entire length of afferent arterioles supplying juxtamedullary glomeruli. During postnatal life the distribution of renincontaining cells progressively shifted to a restricted juxtaglomerular position in afferent arterioles. Simultaneously, density and organization of nerve fibers increased with age along the arterial vascular tree. Our results suggest that innervation of renin-containing cells is present in fetal life and follows the centrifugal pattern of renin distribution and nephrovascular development.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0878
    Keywords: Immunocytochemistry ; Isoactin ; Muscle ; Fetus ; Ontogeny ; Rat (Wistar-Kyoto)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Actin, a cytoskeletal and contractile protein, is expressed in six different isoforms that exhibit striking specificity. No studies have considered the muscle-specific actin expression in multiple organ systems in the intact fetus. Using a monoclonal antibody (B4) which reacts specifically with the isoactins of the smooth and skeletal muscle our immunohistochemical study examined whole fetal body sections to follow the development of actin expression throughout the last third of gestation in the Wistar-Kyoto rat. B4 staining was exclusively localized to muscle, confirming its high specificity and its usefulness for studying the ontogeny of muscle-specific isoactins. At 15 days of gestation, B4 staining was detected in the heart, the thoracic aorta and the skeletal muscle of the chest wall. The distribution and intensity of staining in the heart were initially higher than in the aorta or skeletal muscle and remained unchanged throughout the remainder of gestation, suggesting that the maturation of cardiac actin expression is well developed, although not fully completed before birth. Expression of muscle-specific actins in skeletal muscle was age-dependent and correlated with the maturational changes of muscle cell precursors. B4 staining in the fetal kidney was not apparent until day 20 of gestation and was localized to the inner cortical vessels. in association with the most mature nephrons, suggesting a centrifugal maturation of the intrarenal vasculature. The intensity of B4 staining in most tissues including bronchi, bowel, diaphragm, chest wall muscle and peripheral and pulmonary arteries increased by the end of gestation.
    Type of Medium: Electronic Resource
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