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Toxic Responses of the Kidney
Published in Stephen K. Hall, Joana Chakraborty, Randall J. Ruch, Chemical Exposure and Toxic Responses, 2020
The afferent arteriole delivers blood under high pressure to the glomerulus where selective filtration occurs. Hydrostatic pressure is the primary force responsible for the production of the glomerular filtrate. The filtration barrier consists of (1) the fenestrated endothelial cells lining the glomerular capillary, (2) epithelial podocyte foot processes, and (3) the intervening basement membrane derived from both the glomerular endothelium and supporting epithelial podocytic cells. Since this barrier is composed of cells with holes (fenestrated endothelium) or slits (podocyte foot processes), the selectivity of glomerular filtration is accomplished by the fused basement membranes. Ultrastructurally, the basement membrane has three components. The central layer is electrondense, contains fibers (type IV collagen), and is termed the lamina densa. The two outer most layers are more electron-lucent and are termed lamina rara interna, and externa. Materials which pass through the filter are limited to small molecular size and net molecular charge.
Effects of continuous and pulsatile flows generated by ventricular assist devices on renal function and pathology
Published in Expert Review of Medical Devices, 2018
Takuma Miyamoto, Jamshid H. Karimov, Kiyotaka Fukamachi
Under physiologic conditions, the RAA system is activated in response to decreases in blood pressure or salt and extracellular fluid volume [59]. At the organ level, secretion of renin from juxtaglomerular cells is controlled by a number of factors that become active in the direct vicinity of renin-secreting cells [60]. These factors comprise neurotransmitters released from sympathetic nerve endings, which are found at high density around renin-secreting cells, angiotensin II, autacoids released from endothelial or macula densa cells, various hormones, and the intraluminal blood pressure in afferent arterioles. Renin secretion from the kidneys is inversely related to renal perfusion pressure. Renal baroreceptor mechanisms not only regulate acute renin secretion but also the long-term transformation of vascular SMCs into renin producers.