Abstract
The cytologically demonstrable storage in the retothelial system (RS) has become a model test of its functions. A substance suitable for clearance tests, determination of the pattern of distribution and histological changes of the RS must yield stable, metabolically largely inert colloidal solution of known molecular size; the storage must be reversible without any disturbances; it must be also suitable for quantitative determination and morphological identification. In order to gain criteria for the evaluation of the functional behavior of the RS the fate of 32P labelled K-Na-polyphosphate was investigated in rabbits in serial tests over some period of time. The extrarenal clearance shows in semi-logarithmic representation a straight line as an exponential function of time; the elimination half-life increases with dosage, due to a saturation effect, and may go as far as blockade; excretion in the urine within 10 days is in 20 per cent of the administered activity. The actual pattern of distribution shows about 40 per cent to be present in liver and bone marrow. The intensity of storage was found in the decreasing order of spleen, bone marrow and liver. The turnover of P is obviously most intense in the bone marrow in con-nection with hematopoiesis. The functional capacity of the PS is greatest in the mouse and smallest in the dog, the rabbit being intermediate. Preferred site and intensity of storage vary with different species of animal but are characteristic enough for each species to make possible comparative investi-gations of the RS under varied conditions.
