Filtration in single isolated mammalian glomeruli

Filtration in single isolated mammalian glomeruli. We describe a new method for the study of ultrafiltration in single isolated glomeruli in vitro. Glomeruli without capsules were isolated by a sieving technique at room temperature in isotonic medium containing 4 to 6g of bovine albumin per deciliter. The geometric volume of the glomeruli was reflected in the exchangeable tritiated water space; 70 to 75% of the water space was extracellular, most being intracapillary. When the protein concentration of the bath surrounding a single glomerulus was suddenly reduced, fluid entered the glomerular capillaries osmotically and they swelled. Subsequently, erythrocytes flowed out ofthe broken ends ofthe arterioles at the hilum. Individual erythrocytes could also be observed to move within capillary lumens. The rate of filtration of fluid into the capillary lumens was determined from optical measurements of total glomerular volume following a change in protein concentration of the external bathing medium. The filtration coefficient, K f , was estimated from the initial slope of the relation between volume and time. The K f values for dogs, mature rabbits, immature rabbits, Buffalo rats, and Munich-Wistar rats were 17.03 ± 0.73, 5.57 ± 0.47, 3.70 ± 0.23, 5.97 ± 0.36, and 6.79 ± (SEM) 0.41 nl/min/mm Hg, respectively. The estimated K f values and the size of the glomeruli were proportional among species. These studies show that the hydraulic conductivity of the capillary walls and the hydrodynamic properties ofthe capillary lumens can be determined in single isolated glomeruli. We suggest that this method may be applied to the study of physiologic and pathophysiologic processes in glomeruli of several species including man. La filtration dans des glomerules uniques isoles de mammiferes. Une novelle methode est decrite pour l'etude de l'ultrafiltration dans des glomerules isoles in vitro. Des glomerules ont ete isoles par une techinque d'ecremage a temperature ambiante dans un milieu isotonique contenant 4 a 6 g/dl d'albumine bovine. Le volume du glomerule etait reflete par l'espace de diffusion de 3 H 2 O echangeable; 70 a 75% de l'espace de diffusion de l'eau etait extracellulaire, la plus grande partie etant intracapillaire. Quand la concentration de proteines du bain entourant un glomerule unique est diminuee brusquement, de l'eau penetre osmotiquement dans les capillaires glomerulaires qui gonflent. Puis les erythrocytes s'ecoulent par les extremites rompues des arterioles du hile. On peut observer le mouvement de certains erythrocytes a l'interieur des lumieres capillaires. Le debit de filtration du liquide dans les lumieres capillaires a ete determine a partir de mesures optiques des volumes glomerulaires apres une modification de la concentration de proteines dans le milieu externe. Le coefficient de filtration, K f , a ete calcule a partir de la pente initiale de la relation entre le volume et le temps. Les valeurs de K f pour les chiens, les lapins adultes, les lapins non adultes, les rats Buffalo et les rats Munich-Wistar etaient respectivement de 17,03 ± 0,73, 5,57 ± 0,47, 3,70 ± 0,23, 5,97 ± 0,36 et 6,79 ± (SEM) 0,41 nl/min/mm Hg. Les valeurs de K f estimees et la taille des glomerules etaient proportionnelles parmi ces especes. Ces etudes montrent que la conductivite hydraulique des parois capillaires et les proprietes hydrodynamiques des lumieres capillaires peuvent etre determinees dans un glomerule unique isole. Nous suggerons que cette methode peut etre appliquee a l'etude de processus physiologiques et physio-pathologiques dans des glomerules de diverses especes, parmi lesquelles l'homme.