Distribution of alloxan-C14 in islet and other tissues of the toadfish (Opsanus tau)

Abstract

These studies on the mechanism by which alloxan selectively destroys the ß cells in the islets of Langerhans have been carried out in the toadfish because the islet tissue in this species is segregated into a discrete mass, separated from the acinar tissue. We have measured the C14 content of several tissues at various times after intravenous injection of tracer doses of alloxan-2-C14. The islet C14 content never exceeded 50% of that of blood and was no greater than that found in many other tissues. Thus the selectivity of alloxan is not due to selective concentration by islet tissue. The distribution of alloxan-2-C14 was compared with that of d-mannitol-1-H3. A mixture of both isotopic substances was injected and the C14 and H3 in each tissue determined. The distribution of alloxan-2-C14 was very similar to that of d-mannitol-1-H3. This suggests that tracer doses of injected alloxan do not enter islet cells but remain in the extracellular compartment, and that the ß-cell membrane may be a primary site of alloxan action.