Measurement of plasma volume in rats with use of fluorescent-labeled albumin molecules.
We describe a method for measuring plasma volume (PV) in small animals that allows small sample sizes but does not require the use of radioisotopes and thus is a convenient approach for making repeated measurements. Texas Red covalently bound to albumin (TR-A) was used in a typical indicator-dilution technique to measure PV. The relative fluorescent intensity of TR-A is linear to its concentration (up to 0.15 mg/ml) at an excitation lambda of 590 nm and an emission lambda of 610 nm. Catheters were inserted through the right jugular vein of anesthetized rats and threaded into the vena cava. A 0.5-ml control blood sample was taken, a measured quantity of TR-A was injected, and the catheter was flushed with saline. A 0.5-ml postinjection sample was taken 5 min after TR-A injection. PV was calculated by comparing the difference between the relative fluorescent intensity of control and postinjection plasma samples to a standard. The PV of 22 rats [362 +/- 14 (SE) g] was 14.1 +/- 0.4 ml (39.6 +/- 0.9 ml/kg body wt) measured by the TR-A method and 12.8 +/- 0.4 ml (35.9 +/- 1.0 ml/kg body wt) measured by a standard radioiodinated albumin method. There was a strong correlation between PV measured by both methods in the same rat (r = 0.90, P < 0.01). Infusion experiments indicated that the TR-A method can detect acute changes in PV, and repeated measurements of PV made on a chronically instrumented rat demonstrated that the method can reliably measure PV on consecutive days.
Gillen
C M
CM
John B. Pierce Laboratory, Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06519.
Takamata
A
A
Mack
G W
GW
Nadel
E R
ER
D000818:Animals; D001810:Blood Volume / Q000502:physiology; D004395:Dye Dilution Technique; D005456:Fluorescent Dyes; D006400:Hematocrit; D006863:Hydrogen-Ion Concentration; D008297:Male; D010953:Plasma Volume; D051381:Rats; D017207:Rats, Sprague-Dawley; D012235:Rhodamines; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012711:Serum Albumin, Radio-Iodinated; D013050:Spectrometry, Fluorescence; D014966:Xanthenes
D005456:Fluorescent Dyes; D012235:Rhodamines; D012711:Serum Albumin, Radio-Iodinated; D014966:Xanthenes; D012710:Serum Albumin, Bovine; C034657:Texas red; C050829:sulforhodamine 101