Alpha-2-macroglobulin, albumin, and chymotrypsin inhibitory capacity in cerebrospinal fluid as indices of blood-cerebrospinal fluid barrier.

Concentration of alpha-2-macroglobulin, albumin, and chymotrypsin inhibitory capacity representing mainly alpha-1-proteinase inhibitor were estimated in cerebrospinal fluid in disorders of the central nervous system. While chymotrypsin inhibitory capacity was elevated in all cases with derangement of the blood-cerebrospinal fluid barrier, in 30% of the cases alpha-2-macroglobulin levels were in the normal range. The difference can be attributed to the much larger size of the latter. Better correlation between albumin concentration and chymotrypsin inhibitory capacity (r = 0.84) than between albumin and alpha-2-macroglobulin (r = 0.62) supports the view that the rate of entry of proteins from blood into cerebrospinal fluid is inversely related to their size.