Abstract
A method for the study of non-ionic diffusion of weak bases or acids is described. A solution containing test substance and 25 meq/1 of sodium bicarbonate is adjusted to pH = 7.4 and injected intravenously. The acute non-respiratory changes in extracellular acid-base balance are followed by measuring the plasma bicarbonate concentration at pCO2 = 40 mm Hg (“standard bicarbonate”, st.bic.). A decrease of st.bic. signifies extracellular acidosis and intracellular alkalosis, when the base form of the test substance has passed more rapidly into the cells than the corresponding acid.
The organic bases: Tris(hydroxymethyl)-aminomethan (THAM), ethanolamine (eth.) and 2-methyl-2-amino-1-propanol (MAP) and ammonia (NH,) were tested on rats. With THAM the average st.bic. in meq/l decreased only 0.8 (p > 0.1) while a significant decrease (p < 0.01-0.001) occurred with eth. 2.2, with MAP 2.5 and with NH3 5.4.
Lacking non-ionic diffusion, THAM does not cause a rapid correction of intracellular acidosis, whereas such correction may be expected with other organic bases having better diffusion possibilities in the non-ionized form due to predominance of lipophilic characteristics.