Superficial and juxtamedullary nephron function during saline loading in the dog.
A modification of the microdissection technique of Hanssen was utilized in dogs to measure superficial (SNGFR) and juxtamedullary nephron filtration rate (JMGFR) in control and saline-expanded dogs. During control studies SNGFR was 60+/-4 and JMGFR was 72+/-5 nl/min. During saline loading SNGFR was 74+/-8 and JMGFR was 65+/-6 nl/min. The ratio SNGFR: JMGFR significantly increased from 0.84+/-0.03 to 1.15+/-0.08. Glomerular perfusion rate (GPR) was measured with the microsphere method during control and saline loading. Superficial GPR did not change significantly but juxtamedullary GPR increased from 225+/-42 to 323+/-39 nl/min. Calculated superficial nephron filtration fraction was unchanged after saline expansion but juxtamedullary filtration fraction decreased from 0.34+/-0.07 to 0.24+/-0.07. The data demonstrate a tendency for filtration to shift toward the superficial part and plasma flow toward the deep part of the kidney cortex. GFR in juxtamedullary nephrons appears to be less plasma flow-dependent than in superficial nephrons. The fall in filtration fraction in the deep cortex may affect sodium excretion by juxtamedullary nephrons.
D000818:Animals; D001783:Blood Flow Velocity; D002250:Carbon Radioisotopes; D002587:Cesium Isotopes; D004285:Dogs; D005295:Ferrocyanides; D005374:Filtration; D005919:Glomerular Filtration Rate; D007668:Kidney / Q000502:physiology*; D007672:Kidney Cortex / Q000098:blood supply; D008863:Microspheres; D009399:Nephrons / Q000187:drug effects / Q000502:physiology; D011868:Radioisotopes; D012965:Sodium Chloride / Q000494:pharmacology*; D013326:Strontium Radioisotopes
D002250:Carbon Radioisotopes; D002587:Cesium Isotopes; D005295:Ferrocyanides; D011868:Radioisotopes; D013326:Strontium Radioisotopes; D012965:Sodium Chloride