HUMAN C-PEPTIDE - THE IMPORTANCE OF C-PEP TIDE DETERMINATION AND THE PROBLEM OF ITS BIOLOGICAL-ACTIVITY

The human C-peptide is a fragment of proinsulin (AK 33-63). Proteolyti c splitting off the C-peptide from the proinsulin molecule affords the active hormone, insulin, which is then secreted by pancreatic B-cells into the portal blood together with an equimolar amount of C-peptide. Radioimmunoanalytical determination (RIA) of the C-peptide level in b lood plasma, serum and urine of patients is now the best indirect indi cator of the function of B-cells in pancreas. When compared with the d etermination of insulin, the determination ed C-peptide has a number o f advantages, mainly - in the case of the C-peptide - a varying extrac tion by the liver does not take place and this even enables the examin ation of patients who are treated with exogenous insulin. The RIA C-pe ptide is used mainly in diabetology. The problem of the biological fun ction of C-peptide still remains open. Recently published studies indi cate a certain positive effect of exogenously administered C-peptide t o diabetics of the type on the glomerular filtration, excretion of pro tein in the urine, microvascular function, especially blood flow, capi llary permeability and substrate exchange in the bone muscle. The poss ibility of treating diabetics of the Ist type by administration of exo genous C-peptide would be a great contriburion to the therapy of these patients.