Distribution of interstitial fluid pressure and fluid volumes in hind-limbskin of rats: relation to meridians?

To determine the distribution of interstitial fluid pressure (P-i) and volu me (V-i), and to relate the distribution of these parameters to the distrib ution of potential meridians located by measurement of electrical impedance , we measured P-i, extracellular fluid (V-e) and plasma volumes (V-p) 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. P-i was measured with s harpened glass capillaries connected to a servo-controlled counter-pressure system, while V-e and V-p were determined as the extravascular distributio n spaces of Cr-51-EDTA and I-125-human serum albumin, respectively. V-i was calculated as V-e - V-p, and V-w as the difference between skin wet and dr y weight. Grand mean P-i averaged -0.81 mmHg (SD 0.83, n=95). P-i in skin w as significantly higher in lateral and medial parts of the medial aspect of hind-limb compared to pressures in the intermediate area (P < 0.05). Press ures in the concave groin and the convex knee area were more negative and p ositive, respectively, than in the flat intermediate central hind-limb area . There was a significantly higher V-i (P < 0.05) and V-w (P < 0.05) in the lateral side than that in the medial side. V-p was higher medially and lat erally than in the intermediate area (P < 0.05 for both comparisons), and c orrelated positively and significantly with P-i (r=0.66, P < 0.05). No corr elation was found between P-i and electrical impedance. The study suggests that the distribution of P-i, V-i, V-p and V-w is heterogeneous in hind-lim b skin at a macroscopic level without obvious relations to potential meridi ans.