Figure 3. Representative plots of glomerular volume change versus time since perifusate switch.

A, volume change displayed by one glomerulus, in response to ‘dilute to concentrated’, then ‘concentrated to dilute’ switch of solutions. i–ii, glomerulus volume is stable when surrounded by dilute perifusate (1% BSA); ii, perifusate switch to concentrated BSA (8%) reduces glomerular volume by 10% (iii); glomerular volume then stabilizes (iv) (equilibration); v, glomerular swelling on re-introduction of ‘dilute’ perifusate (vi). B, fluid egress from isolated glomerulus (filtration): initial rate of reduction of glomerular volume when exposed to 8% BSA (oncotic gradient 29.2 mmHg). The slope of regression line is set at zero (a). The direction of fluid movement out of the glomerulus is in the same direction as glomerular filtration (slope of line b =−1.125 nl s⁻¹). C, fluid ingress into isolated glomerulus (reabsorption): application of a 9.8 mmHg oncotic gradient induces glomerular swelling (slope of line b = 0.240 nl s⁻¹).