Microvascular permeability transients due to histamine in cat limb
Wolf, M.B.; Scott, D.R.; Watson, P.D.
American Journal of Physiology 261(1 Pt 2): H220-H228
1991
ISSN/ISBN: 0002-9513 PMID: 1858924 Document Number: 370656
We measured the protein solvent drag reflection coefficient (.sigma.f) and the capillary filtration coefficient (CFC) before and after adding 1 or 10 .mu.M histamine to the recirculating fluid (20% plasma, remainder albumin and electrolytes, hematocrit of 1-2%) perfusing the isolated cat hind-limb preparation. Transient .sigma.f measurements were made at 3- to 15-min intervals after histamine using a modification of the steady-state integral-mass balance method. CFC measurements were made at .apprx.10-min intervals after histamine in separate experiments. A 1 .mu.M dose of histamine caused .sigma.f to fall from .apprx.0.8 to .apprx.0.3 in 2-3 min; .sigma.f then returned to control in .apprx.20 min. CFC response to the 1 .mu.M histamine was a peak increase .apprx.2 times control and a return to control in .apprx.40 min. A 10 .mu.M dose caused .sigma.f to fall rapidly to near zero. In general, recovery was much slower than for the 1 .mu.M dose, most of the limbs not returning the control by 40 min after histamine. CFC measurements after 10 .mu.M histamine increased only .apprx.5 times control even though .sigma.f was near zero at the same time. CFC remained above control for .apprx.60 min. The combined .sigma.f and CFC data could be described quantitatively if histamine simultaneously opened both short-lived large gaps (.apprx.1,000 .ANG.) and a longer-lived pathway that sieved protein like the normal pathway and if the numbers of channels of each pathway closed exponentially with 4- and 15-min time constants, respectively. The maximum number of gaps open was nonlinearly dose dependent. Also, the presence of a barrier in series with the endothelial membrane was suggested by the CFC limitation in the presence of a very low .sigma.f.