Effect of KCN, antimycin A, and glucose on absorption spectra. Representative spectra obtained from 600 rat islets perifused
in MEM are shown. When cytochromes in the islets were fully reduced by the addition of cyanide, valleys centered around 551
nm for cytochrome c and 605 nm for cytochrome a3 were well resolved (A). In contrast, in the presence of antimycin A, a blocker of cytochrome b, electrons were prevented from transferring to cytochrome
c and both valleys were not detectable (B). At low glucose, only the cytochrome c valley is detectable (C), which increases in depth at 20 mmol/l glucose (D). Each spectrum shown is the average of 55 acquisitions, each with an integration time of 50–150 ms.