Angiotensin II production and distribution in the kidney: I. A kinetic model.
Information on the levels of angiotensin II (Ang II) and its receptors in the various renal tissue compartments is still incomplete. A model is presented describing the kinetics of Ang II production, distribution, and disposal in the renal cortex. Basic features are: (1) the model is designed to derive, from Ang II measurements in blood and in whole tissue, estimates of the local densities of the Ang II type 1 (AT(1)) and type 2 (AT(2)) receptors, and to calculate the concentrations of endocrine and paracrine Ang II they actually 'see'; (2) glomerular and peritubular tissue are conceived as separate regions (glomerular region (Glom), peritubular region (Pt)); (3) in Glom and in Pt, Ang II is homogeneously distributed in capillary blood and in interstitial fluid; (4) the model allows for local Ang II concentration gradients between interstitium and blood; (5) Ang II from the circulation diffuses into the interstitium of Glom after convective transcapillary transport; (6) Ang II produced in tubules or Pt enters the microcirculation through diffusive overflow from interstitium; (7) the presence of cell-surface-bound Ang II depends on the reaction with AT(1) and AT(2) receptors, and the presence of intracellular Ang II depends on the internalization of Ang II - AT(1) receptor complex; and (8) the model provides for glomerular filtration, vasopeptidase-mediated degradation, and intracellular degradation as mechanisms of elimination. This model can serve as a framework for detailed quantitative studies of the renin-angiotensin system in the kidney.
Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands.
M A D H
MA
Schalekamp
A H J
AH
Danser
D000804:Angiotensin II / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D006801:Humans; D007668:Kidney / Q000098:blood supply / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D044139:Receptor, Angiotensin, Type 2 / Q000378:metabolism; D012079:Renal Circulation; D012084:Renin-Angiotensin System
D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D000804:Angiotensin II