Modeling the effects of medullary blood flow regulation on pressure natriuresis

Abstract

The regulation of medullary blood flow by the vasoactive decending vasa recta may play an essential role in pressure natriuresis. While the regulatory mechanism remains incompletely understood, and quantities such as the absolute medullary blood flow remain experimentally inaccessible, many factors involved in that regulation have been identified. We present a whole‐kidney model of water and sodium balance that encompasses the renal vasculature and a population of superficial and juxtamedullary nephrons, each of which has a separate juxtaglomerular apparatus and autoregulates autonomously. Vasoconstriction of the vasculature and the epithelial transport are regulated by plasma hormone levels. Model predictions are consistent with acute renal function curves obtained from in vivo studies of the rat under a wide range of physiological conditions. We use this model to investigate the effects of vascular vasoconstriction and medullary blood flow regulation on the kidney's ability to produce concentrated urine at high arterial pressures. These findings are evaluated against the known and hypothesized actions of the known regulatory mechanisms. This research was supported in part by NIH grant DK‐89066.