Centrifugal and activation methods for rapid identification of lysosomotropic drugs with the use of rat liver homogenates.

emptied and washed, and the 24h efflux of inulin was determined; it is plotted against the final swelling ratio from the experiment in which the sac was stretched. An unstretched control is also included. In a similar unstretched sac, the half-time of raffinose escape was I4Omin. Clearly inulin escapes faster than the polyethylene glycol of comparable molecular weight at all porosities, but at least 10 times slower than rafhose. In further experiments inulin and polyethylene glycol were dialysed together. The results confirmed that inulin efflux significantly exceeds polyethylene glycol efflux, and that the latter is concentration dependent. However, they showed much less effect of sac stretching on inulin efflux, indicating an interaction between inulin and polyethylene glycol efflux. In the shortest of these experiments (24h) the mean ratio of inulin to polyethylene glycol efflux was 6.4; the ratio of initial escape rates might therefore be much greater. In conclusion, the escape rate of inulin is at least six times that of polyethylene glycol 6000 at all the porosities studied. For comparison with this value, it can be estimated from Figs. 1 and 2 that, under comparable conditions, the efflux of polyethylene glycol 4OOO is about three times that of polyethylene glycol 6000, and inulin efflux is about twice that of polyethylene glycol 4000. The elution of 95 % of the inulin in 1.3 times the void volume of Sephadex G-25 indicates a mean molecular weight of at least 5500 (cf. Phelps, 1965). It is therefore apparent from the results that polyethylene glycols do not pass in an appreciably extended configuration through membranes of porosity comparable with the renal glomerular membrane. They also show that inulin passes through a cellophane membrane much more rapidly than would be expected from its molecular volume of rotation, but at 0.1 or less of the rate for raffinose, which can be considered as a sphere of diameter equal to the thickness of inulin.