Extravascular transport of fluorescently labeled albumins in the rat mesentery.
OBJECTIVE
Fluorescently labeled albumin is used frequently as a tracer when monitoring microvascular permeability. Several fluorescent dyes are available for labeling protein, including fluorescein isothiocyanate (FITC) and Texas Red (TR). Because differences in leakage of dye-labeled proteins have been reported, the objective of the present study was to compare the accumulation of these two tracers in interstitium and lymph after the inflammatory event of ischemia-reperfusion.


METHODS
Anesthetized rats were injected intravenously with FITC-labeled albumin (FITC-alb) and TR-labeled albumin (TR-alb) before 30 minutes of mesenteric ischemia. Because the tracers leaked out of the microcirculation after reperfusion, accumulation in the surrounding buffer-superfused tissue, and in separate experiments, accumulation in lymph vessels, was defined as the ratio of tissue-to-plasma and lymph-to-plasma fluorescence.


RESULTS
Reperfusion induced a significant increase in tissue-to-plasma fluorescence of FITC-alb; however, no increase was observed for TR-alb. In contrast, lymph-to-plasma fluorescence of TR-alb tended to be greater than FITC-alb. Reperfusion-induced increases in tissue-to-plasma fluorescence of TR-alb occurred only when the superfusate was replaced with mineral oil, in which case tissue-to-plasma TR-alb fluorescence tended to be greater than FITC-alb.


CONCLUSIONS
Measurement of fluorescently labeled albumin leakage from mesenteric venules depends on the dye used to label the albumin and requires an assessment of losses from the extravascular measuring region.
Harris
Norman R
NR
Department of Bioengineering, Pennsylvania State University, University Park, PA 16802-6804, USA. NRH1@PSU.EDU
Whitt
Stevan P
SP
Zilberberg
Jenny
J
Alexander
J Steven
JS
Rumbaut
Rolando E
RE
D000418:Albumins / Q000493:pharmacokinetics*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002199:Capillary Permeability; D004643:Emollients / Q000494:pharmacology; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D007511:Ischemia / Q000378:metabolism* / Q000503:physiopathology; D008196:Lymph / Q000378:metabolism; D008297:Male; D008643:Mesentery / Q000098:blood supply* / Q000378:metabolism*; D008899:Mineral Oil / Q000494:pharmacology; D010477:Perfusion; D051381:Rats; D011916:Rats, Inbred F344; D015427:Reperfusion Injury / Q000378:metabolism* / Q000503:physiopathology; D014966:Xanthenes
D000418:Albumins; D004643:Emollients; D005456:Fluorescent Dyes; D014966:Xanthenes; D008899:Mineral Oil; C034657:Texas red; D016650:Fluorescein-5-isothiocyanate