Gilg, Albert

Horster, Michael

Lory, Peter

English

University of Regensburg Publication Server

© INFLUENCE OF ION TRANSPORT AMD CORTICO-MEDULLARY CYTOARCHI-TECTURE ON SOLUTE CONCENTRATIONS IN THE DIFFERENTIATING KIDNEY: PREDICTIONS FROM A MODEL SIMULATION ANALYSIS. Hors ter,M.,Ci Ig,A.,Lory,P. Physiologisches I n s t i t u t der Universität und Ins t . fur Mathematik der TU,D-8000 München The capacity of the medullary countercurrent system for os-motic concentration of f i n a l urine increases with ontogeny. The r e l a t i v e contr ibut ions of d i f f e ren t morphological and transport parameters to th i s process can not be evaluated experimentally. The present model incorporates, in pa r t i cu -l a r , changes of ion transport in the d i f f e r e n t i a t i n g neph-ron (1), ontogenetic a l te ra t ions of the microarchitecture of outer (OM) and inner (IM) medulla (2), and re-entry of urea from the pe lv i s into medullary i n t e r s t i t i um (3,4). Three developmental phases were computed:(i ) low ion trans-port rate in TAL,most loops turning in c o r t e x ; ( i i ) i n t e r -mediate ion transport rate in TAL, entry of most loops i n -to outer medulla; ( i i i ) f i n a l s tate of funct ion. Results, (i ) Central core (CC) MaCl (mmol-H) i s almost constant, CC urea r i ses s l i g h t l y at t r an s i t i on OM/IM. ( i i ) CC NaCl increases by a factor of 2 in OM and CC urea by a fac to r of 5 in OM. ( i i i ) CC MaCl r i ses by a fac to r of more than 3 in OM, to ta l osmotic a c t i v i t y by a factor of almost 4 in OM, to reach 1200 mosnvl"' ' in IM. The data agree with measured values. Conclusions. Ontogeny of renal osmotic work depends on two primary fac tor s : the increasing ion transport capacity of the th ick ascending loop of Henle (TAL) and the descend of c o r t i c a l loops of Henle into the medulla to provide fo r the sequestration of previously concentrated urea. The model w i l l be appl ied to predict the e f fec t of var ia t ions of i n -d iv idua l components, such as induced ion transport or osmo-t i c water permeabil ity in the d i s t a l nephron,upon the e f f i -cacy of medullary osmotic work. (1) Hörster, M. Amer.J.Physiol. 325: F387-F394J978 (2) Spe l l e r , A.M.,Moffat,D.B. J.Anat. 123:487-500,1977 (3) Schmidt-Nielsen,B. et al.,Kidney Int.18:419-432,1980 (4) Bonventre,J.V.et al.,Amer.J.Physiol.239:F609-618, 1980 

Influence of ion transport and cortico-medullary cytoarchitecture on solute concentrations in the differentiating kidney: predictions from a model simulation analysis

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Influence of ion transport and cortico-medullary cytoarchitecture on solute concentrations in the differentiating kidney: predictions from a model simulation analysis

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