Glucagon indole method

SELECTIVE HISTOCHEMISTRY OF GLUCAGON IN THE A CELLS OF PANCREATIC ISLETS BY INDOLE METHODS ... 

Up to now attempts to provide a selective morphological detection of glucagon in the A cells of pancreatic islets have been carried out by means of im-munohistochemicaI techniques or indole methods. By immunohistochemistry the presence of glucagon in the cytoplasm of some islet cells has been definitively ascertained, but the exact nature of these cells has not been completely established (Baum et al., 1962 Chiappino et al., 1963). In fact, the most reliable and selective methods for islet cytology are not appliable to fresh cryostatic sections which are required by im-munoh i stochemi caI techniques. 

By indole methods it has been observed that secretory granules of A cells store protein(s) with reactive tryptophan, while both B and D cells do not react (Levine and Glenner, 1958 LogothetopouI os and Salter, I960 Petersson and Heilman, 1963 Solcia and Sampietro, 1965). However, the positivity of A cells to these methods is very weak, fail to occur in some animal species and do not prove per se that the reactive protein is in fact glucagon. We have recon-... 

The reaction has been used to introduce a thiol group in the 2-position of a number of indole-containing compounds, in particular tryptamine, serotonin, skatole and tryptophan, the yields ranging from 65 to 95 per cent (727, 431). The single tryptophan residue of the pancreatic peptide hormone glucagon (29 amino acids) has also been modified by this method to the thioxindolylalanine derivative (727). 

---