snímek PPT
The concept of renal clearance: The effectivity of renal activity could be assesed by means of the amount of a substance which a hypothetical volume of plasma is completely got off per time interval.
It is evident that a completely cleared volume of plasma Cx had to bear the same “load” as the same volume of plasma before did, therefore the amount of the substance which had to be cleared per minute is CX * PX. This amount must be discarded by the kidneys:
This is valid regardless the ways of excretion or reabsorption.
Substances behave differently in the tubulus (Fig. 10) and accordingly, their clearance has a different relationship to GFR (Fig. 11 – 13)