Measurement of single nephron filtration rate in the kidney of the river lamprey, Lampetra fluviatilis L.
1. The reliability of [3H]inulin as a reference substance for the measurement of glomerular filtration rate (GFR) in river lampreys was investigated. 2. Simultaneously measured renal clearances of [3H]inulin and [14C]-polyethylene glycol (PEG) were not significantly different. 3. Recoveries of [3H]inulin in the urine following its injection into the proximal tubule and urinary duct averaged 83.5+/-4.0% (n = 14) and 93.0+/-4.6% (n = 9) respectively. 4. No evidence was obtained to suggest penetration of the tubular wall by by [3H]inulin following its introduction into peritubular capillaries. 5. Gel-filtration of lamprey plasma and urine produced no signs of any significant degradation of the inulin to fructose. 6. [3H]inulin recoveries, though significantly below 100% (P less than 0.001), were considered adequate to justify its use after allowing for possible sources of error. 7. A mean single nephron filtration rate (SNGFR) value of 7.02+/-0.27 nl/min (n = 89) was obtained from the kidneys of anaesthetized freshwater lampreys. 8. [51 Cr]EDTA was found to be totally unsuitable for the measurement of GFR in this species.
D000818:Animals; D005399:Fishes / Q000502:physiology*; D005618:Fresh Water; D005919:Glomerular Filtration Rate; D007444:Inulin / Q000378:metabolism / Q000494:pharmacology; D007668:Kidney / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D007798:Lampreys / Q000502:physiology*; D008722:Methods; D009399:Nephrons / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000378:metabolism
D011092:Polyethylene Glycols; D007444:Inulin