Nw. Scottdouglas et al., MEASUREMENT OF INTESTINAL VASCULAR CAPACITANCE IN DOGS - AN APPLICATION OF BLOOD-POOL SCINTIGRAPHY, Journal of applied physiology, 78(1), 1995, pp. 232-238
To define relative changes in intestinal vascular capacitance, we deve
loped a model that allowed us to construct intestinal vascular pressur
e-volume relationships (PVR). Thirteen a:chloralose-anesthetized and s
plenectomized dogs were studied using a pneumatic constrictor and a sm
all catheter to change and measure portal venous pressure. A small lea
d sheet was placed beneath the abdominal wall. Relative changes in int
estinal blood volume (IBV) were determined by in vivo blood pool scint
igraphy with Tc-99m-labeled erythrocytes and were expressed as percent
ages corrected for specific activity and abdominal wall radioactivity.
PVRs were constructed using data recorded during graded inflations of
the portal venous constrictor. The abdominal wall contributed 32.4 +/
- 7.7% (SD) of the total counts. During a 4-h control period, PVRs var
ied by no more than 6% (of IBV). In the isolated intestinal circulatio
n, the change in IBV was precisely proportional to the volume of blood
added, indicating that this method can detect very small changes in v
olume (less than or equal to 5 mi). Nitroglycerin (25 mu g . kg(-1) .
min(-1)) increased capacitance by 20%. Although it measures only relat
ive changes, the model is stable and sensitive, provides reproducible
measurement of intestinal PVRs, and, with adaptation, may prove useful
in patient studies.