title: Distribution of interstitial fluid pressure and fluid volumes in hind-limb skin of rats: relation to meridians?
abstract: To determine the distribution of interstitial fluid pressure (Pi) and volume (Vi), and to relate the distribution of these parameters to the distribution of potential meridians located by measurement of electrical impedance, we measured Pi, extracellular fluid (Ve) and plasma volumes (Vp) in 14 pre-defined skin areas, 2 x 2 mm, and in concave and convex regions on the hind-limb and groin of rats in control conditions. Pi was measured with sharpened glass capillaries connected to a servo-controlled counter-pressure system, while Ve and Vp were determined as the extravascular distribution spaces of 51Cr-EDTA and 125I-human serum albumin, respectively. Vi was calculated as Ve - Vp, and Vw as the difference between skin wet and dry weight. Grand mean Pi averaged -0.81 mmHg (SD 0.83, n=95). Pi in skin was significantly higher in lateral and medial parts of the medial aspect of hind-limb compared to pressures in the intermediate area (P<0.05). Pressures in the concave groin and the convex knee area were more negative and positive, respectively, than in the flat intermediate central hind-limb area. There was a significantly higher Vi (P<0.05) and Vw (P<0.05) in the lateral side than that in the medial side. Vp was higher medially and laterally than in the intermediate area (P<0.05 for both comparisons), and correlated positively and significantly with Pi (r=0.66, P<0.05). No correlation was found between Pi and electrical impedance. The study suggests that the distribution of Pi, Vi, Vp and Vw is heterogeneous in hind-limb skin at a macroscopic level without obvious relations to potential meridians.
authors.affiliation: Institute of Acupuncture and Moxibustion, China Academy of Traditional Chinese Medicine, Beijing, China.
authors.forename: W B
authors.initials: WB
authors.lastname: Zhang
authors.forename: K
authors.initials: K
authors.lastname: Aukland
authors.forename: T
authors.initials: T
authors.lastname: Lund
authors.forename: H
authors.initials: H
authors.lastname: Wiig
mesh_terms: D000818:Animals; D017097:Electric Impedance; D005110:Extracellular Space / Q000502:physiology*; D005260:Female; D018495:Fluid Shifts / Q000502:physiology*; D006614:Hindlimb / Q000294:innervation / Q000502:physiology; D008297:Male; D016740:Meridians; D011312:Pressure; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000294:innervation