EFFECTS OF IONS ON VASCULAR SMOOTH MUSCLE 



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Sample analyses of nonvascular smooth muscle are presented for illustration. Estimate of variance is omitted wherever 

 original data were recalculated to fit the tabular description. Derived data depend on either inulin or chloride spaee value 

 shown on same horizontal line. (Table prepared by Dr. F. A. Sreter.) 



Tissue analyses have also been carried out in an 

 attempt to measure Na, K, and water and their 

 extracellular/intracellular partition under a variety 

 of conditions. Few of these have encompassed a 

 representative vascular tissue, and even these few 

 have been quite incomplete. Table 4 presents basic 

 data taken from the work of several laboratories. 



Total aorta Na and K. vary from about 200 to 350 

 and 95 to 150 meq per kg dry tissue, respectively, the 

 variation probably reflecting the animal's age, pre- 

 vious diet, and the sampling method. An aorta sodium 

 so much higher than potassium is consistent with a 

 large extracellular space. 



It is apparent that the chloride space sometimes 

 exceeds the readily measured total water content of 

 the tissues and hence is a poor measure of extracellular 

 space. Tobian & Binion (196), for example, reported 

 an extracellular fluid volume based on chloride which 

 recalculates to some 750 ml per kg wet tissue and this 

 exceeds most investigators' estimates of total water. 

 Dodd & Daniel (49) reported a chloride space of 633 

 and a sodium space of 650 ml per kg rabbit aorta, and 

 again the total tissue water was only 640 to 660 ml 



per kg. They argued that there was probably a frac- 

 tion of bound chloride wrongly included in the calcu- 

 lation. Even after a correction for this, however, they 

 still obtained an extracellular fluid volume of 483 

 ml per kg. 



Using inulin in a revised procedure we estimate 

 extracellular space as about 50 per cent of the total 

 tissue water. This compares favorably with the esti- 

 mate of Prosser et al. (161) of 39 per cent of the total 

 tissue volume. 



The ratio of extracellular to total water runs lower 

 in other types of smooth muscle than in aorta. Inulin 

 space measures 1 2 per cent of the total water in cat 

 small intestine (9) and 34 per cent in the rabbit 

 uterus (39). These again are in line with the electron 

 microscopic observations. [The high inulin space re- 

 ported for the immature cat uterus (39) is out of line.] 



Intracellular Na runs higher in the aorta and in 

 other types of smooth muscle than in skeletal muscle. 



MEASUREMENT OF OSMOTIC PRESSURE AND PH. The 



development of techniques suitable for measurement 

 of osmotic pressure and pH in small samples has made 



