OSMOTIC CONSTITUENTS OF THE BLOOD PLASMA AND PARIETAL MUSCLE OF SQUALUS ACANTHIAS L

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Abstract
Comprehensive analyses of the osmotic consituents of plasma and muscle of Squalus acanthias have been made. In plasma mean concentrations of ions and molecules (mg-ions or mM per kg water) were Na 296. K 7.2, Ca 2.95, Mg 3.48, NH4 0.4, Cl 276, SO4 3.11, HCO3 6.8, lactate 7.2, urea 308, trimethylamine oxide (TMAO) 72.4, amino-N 11.6, total NPN 838 mg-atoms. In muscle mean concentrations were Na 42.4, K 119, Ca 2.09, Mg 12.9 Cl 35.9, SO4 1.24, lactate 23.8, total P (mg-atoms) 91.3, urea 333, TMAO 180, betaine 100, creatine 68.2 (26% bound as creatine phosphate), amino-N 108, NH4 4.7, total NPN 1447 mg-atoms. In other specimens fractionation of the acid-soluble compounds in muscle gave inorganic P 28.0, creatine phosphate 23.9, ATP 9.6, remaining phosphate 22.9 (total 84.4 mg-ions). Using osmotic coefficients calculated osmotic concentration of muscle exceeded that of plasma, and possible reasons for this are discussed. Directly determined osmotic concentrations were sea water 965, plasma (6 ♂♂) 993, and muscle juice 1023 milliosmoles. Some estimates of intracellular ionic concentrations were obtained from measurements of inulin space in muscle. Analysis of muscle juice enabled approximate estimates of ion-binding. About half the Na and Ca and nearly one fifth of the Mg in muscle cells appears to be bound, but little of the Cl and K.

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