Evidence-Based Evolutionary Medicine by John S. Torday & Neil W. Blackstone & Virender K. Rehan

Author:John S. Torday & Neil W. Blackstone & Virender K. Rehan
Language: eng
Format: epub
Published: 2018-07-31T00:00:00+00:00

The Kidney Glomerulus as a Homolog of the Lung Alveolus

The kidney glomerulus is the site of fluid and electrolyte homeostatic control. The glomerulus is lined by epithelial podocytes that synthesize and secrete PTHrP (Figure 5.2). The secreted PTHrP binds to its receptor on the specialized fibroblasts that underpin the kidney tubules, called mesangial cells. Fluid distension of the glomerulus stimulates PTHrP production, stimulating mesangial secretion of fluid and electrolytes into the kidney tubule. This mechanism is homologous with the effect of air distension of the alveolus, stimulating surfactant production by the alveolar type II cell, maintaining alveolar homeostasis by reducing alveolar surface tension. As an aside, in the womb both the alveolus and the glomerulus produce amniotic fluid. Postnatally, the alveolus and glomerulus act synergistically to maintain allostasis.

It is important to point out that the barotrauma of hypertension can inhibit the PTHrP signaling between the podocytes and the mesangial cells, causing glomerular scarring, just as it does alveolar fibrosis due to over‐distension of the lung.

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