Inulin space and fibre size of stimulated rat muscle

Abstract

If a limb of an anaesthetized animal is intermittently tetanized for a few minutes, the muscles soon become swollen, turgid and pink, and the water content increases considerably. Such effects might be produced by swelling of the fibres or by extracellular and circulatory changes. In this study it is shown that the increased inulin space partly accounts for the rise in water content on stimulation. In addition, measurement of fibre diameter showed no significant increase after tetanization. These results have also been used to calculate internal ion concentrations. METHODSInulin 8pace. Mature rats were anaesthetized with ether, nephrectomized, and 2 ml. of a warm supersaturated solution of inulin (25 %, w/v) which had previously been filtered, was injected into the external jugular vein. The rats were allowed to recover. After 2-5 hr, sodium amylobarbitone was injected into the peritoneal cavity, 0.1 ml. of a 10% (w/v) solution per 100 g being used. In some cases, the sciatic nerve was then stimulated. Blood and gastrocnemius muscle were later removed. Visible fat was cut away from the muscle, and the latter was usuallydividedintotwo, half being retained for estimation of water and cations, while the other half was required for estimation of inulin in muscle and plasma using the procedure of Ross & Mokotoff (1951). Blank values, obtained by dummy experiments without inulin, were subtracted in each case. It was found that a larger dose of barbiturate diminished the response of the muscle to stimulation and there was then no increase in the inulin space.Blood content. Blood in muscle was estimated as alkaline haematin, as used by Conway & Fearon (1944), the colorimetric procedure being that described by Boyle, Conway, Kane & O'Reilly (1941). The blank value, which was equivalent to 1F7 g/100 g, was obtained from the gastrocnemius muscle after perfusion with Krebs solution (saline) for 3 hr, which may have removed some myoglobin.Stimulation. The sciatic nerve of a rat, anaesthetized as above, was exposed and stimulated during each alternate second; a succession of single maximal shocks at a rate of 10/sec was employed to produce intermittent incomplete tetani. A constant-current stimulator with a rectangular-shaped output was used (Bernstein, 1950), with duration 0-5 msec. A load of 5% body weight was attached to the leg, and the latter operated a lever whose excursions were recorded on a slow drum. Intermittent tetanization was continued for 30 min. This method of

Diffusion of labelled substances through isolated rat diaphragm

“…The extracellular space in the rat diaphragm tends to increase with time, even in thin diaphragms maintained in vitro under favourable conditions (Creese & Northover, 1961). The muscle fibres themselves do not seem to undergo a detectable change in volume (Creese, 1954;Creese, D'Silva & Hashish, 1955). In this context the present findings, that the thickness of the diaphragms increases with time and that the tortuosity of the diffusion channels through the extracellular compartment decreases greatly, are explicable at least on a qualitative basis.…”

Structural biomechanics modulate intramuscular distribution of locally delivered drugs

“…To date much work on intramuscular transport has focused on measuring volumetric changes in interstitial space or total tissue volume induced by strain or contraction using tritiated water (Cappelli et al, 1981); molecular markers like inulin (Cappelli et al, 1981, Creese et al, 1955); albumin (Baker and Davis, 1974, Ward et al, 1996); or solutes like EDTA (Ward et al, 1996), sodium, and potassium (Sreter, 1963a, 1963b). Studies have measured contraction-induced diffusion of water (Trombitas et al, 1993) or myoglobin (Papadopoulos et al, 2000), but only intracellularly in single myofibers.…”

Heterogeneities in regional volumes of distribution and flows in rabbit heart

“…O'Keefe et al (36) have attempted to use histological point-counting methods to this end, estimating that the capillary-to-large-vessel volume ratios were ~27.2:4.9 or over 5-fold in normal dogs and 26.8:5.8 or ~4.5-fold in hypertrophied hearts. It would be useful to know the constancy of V ISF /V P , especially for organs with highly variable flow; for example, Creese et al (15) observed large changes in both inulin space (V ECF and blood space in stimulated skeletal muscle. Another source of variation is the form and stage of development of the organ; e.g., Burr and McLennan (14) observed that the interstitial space is much larger in small skeletal muscles than in large ones.…”

“…It is close to the value of 0.956 obtained by Effros and Chinard (16) for dog plasma. Therefore the interstitial water content (V ISF W ) would be 0.95 V ISF and cellular water (V CW ) would be (15) where 0.73 is the water content of erythrocytes in the dog (16).…”