Abstract
In rats 131I-labelled serum albumin can be detected in extravascular tissues within one minute of intradermal injection of histamine.
The rate of accumulation of labelled protein is approximately constant during the period 0-15 minutes after histamine injection. During the first 3 minutes of this period, the protein content of accumulating oedema fluid is substantially less than that of plasma, but the results allow no conclusion as to the composition of oedema formed at later stages of the reaction.
Concurrent or recently completed emigration of leucocytes into the site of histamine injection has no effect on the rate of escape of the labelled albumin. This finding suggests that the vascular basement membrane does not significantly delay protein leakage from histamine-stimulated vessels.