Osmotic constitutents of the blood plasma and parietal muscle of Squalus acanthias L.

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.