TY - JOUR
T1 - Developmental changes in rabbit juxtamedullary proximal convoluted tubule water permeability
AU - Quigley, Raymond
AU - Baum, Michel
PY - 1996
Y1 - 1996
N2 - The mammalian proxi-mal tubule reabsorbs the bulk of the glomerular filtrate in a nearly isosmotic fashion due to the high osmotic water permeability (Pf) of this segment. Although the characteristics of proximal tubule water transport have been studied in the adult proximal tubule, little is known about the neonatal segment. The present study directly measured the Pf and diffusional water permeability (PDw) of neonatal (10 ±2 day old) and adult rabbit juxtamedullary proximal convoluted tubules (PCT) using in vitro microperfusion. The Pf of neonatal juxtamedullary PCT was greater than the Pf of adult juxtamedullary PCT. In contrast, the PDw was not different between the two groups. The Pf and PDw values of both neonatal and adult tubules were inhibited to the same degree by p-chloromercuribenzene sulfonate and had identical activation energies. The transepithelial reflection coefficients of NaCl and NaHCO3 were also found to be similar in both the neonatal and adult proximal tubules. Thus neonatal and adult juxtamedullary PCT have many characteristics of water transport that are identical; however, neonatal Pf is three to five times that of the adult value. This difference in Pf with identical PDw values may give an insight into the transepithelial pathway for water movement in the neonatal tubule.
AB - The mammalian proxi-mal tubule reabsorbs the bulk of the glomerular filtrate in a nearly isosmotic fashion due to the high osmotic water permeability (Pf) of this segment. Although the characteristics of proximal tubule water transport have been studied in the adult proximal tubule, little is known about the neonatal segment. The present study directly measured the Pf and diffusional water permeability (PDw) of neonatal (10 ±2 day old) and adult rabbit juxtamedullary proximal convoluted tubules (PCT) using in vitro microperfusion. The Pf of neonatal juxtamedullary PCT was greater than the Pf of adult juxtamedullary PCT. In contrast, the PDw was not different between the two groups. The Pf and PDw values of both neonatal and adult tubules were inhibited to the same degree by p-chloromercuribenzene sulfonate and had identical activation energies. The transepithelial reflection coefficients of NaCl and NaHCO3 were also found to be similar in both the neonatal and adult proximal tubules. Thus neonatal and adult juxtamedullary PCT have many characteristics of water transport that are identical; however, neonatal Pf is three to five times that of the adult value. This difference in Pf with identical PDw values may give an insight into the transepithelial pathway for water movement in the neonatal tubule.
KW - Diffusional water permeability
KW - In vitro microperfusion
KW - Osmotic water permeability
KW - Reflection coefficients
KW - Volume absorption
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U2 - 10.1152/ajprenal.1996.271.4.f871
DO - 10.1152/ajprenal.1996.271.4.f871
M3 - Article
C2 - 8898017
AN - SCOPUS:0029859513
SN - 0363-6127
VL - 271
SP - F871-F876
JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
IS - 4 40-4
ER -