The Serum Protein Complex as a Factor in Regulating Blood Volume. ∗

Abstract

The most important function of serum protein resides in its osmotic attraction for water. 1 This complex is the most effective agent in maintaining the fluid balance between the blood and the intercellular tissue spaces and serous cavities. Thus, Whipple and his associates 2 have reported that intensive and prolonged plasmapheresis results in symptoms resembling those of shock. For the most part, blood volume determinations were not attempted, but the probable explanation of these observed shock reactions is that the reduction of the serum protein concentration prevents the retention of fluid in the vessels in the face of a normal blood pressure. The importance of the colloidal osmotic pressure of the plasma in maintaining a normal blood volume has been emphasized by Stanbury and coworkers. 3 They have demonstrated that the substitution of gum acacia for the serum protein complex results in no obvious disturbances of water balance in the mammalian body. The present communication is intended to throw additional light upon factors regulating blood volume.

In our investigations 4 , 5 , 6 of the influence of various dietary factors upon the regeneration of serum protein, plasmapheresis was performed quantitatively. Accordingly, the blood volume of the experimental animal was determined periodically as a prerequisite to the calculation of the amount of blood to be withdrawn at each plasmapheresis. The frequency and size of the bleedings were also dependent upon the level of the serum protein concentration, as determined daily. In our study, 55 blood volume estimations were carried out on 3 dogs. On these same days the serum protein concentrations, plasma volumes and cell volumes were also recorded. The methods employed have been described elsewhere. 4