The electron transport chain of serotonin-dense granules of platelets

An electron transport chain has been found and partially characterized in highly purified membranes of serotonin granules isolated from porcine platelets. In these membranes NADH, but not NADPH, is oxidized when ferricyanide or catalytic amounts of cytochrome c were present. The reduced minus oxidized spectrum of these serotonin granule membranes shows a characteristic cytochrome b spectrum with absorbance maxima at 428, 530, and 561 nm. Ascorbate and, at slower rates, NADH are electron donors to cytochrome b561. It is concluded that the electron transport chain present within the membranes of serotonin granules is virtually identical with that of chromaffin granules, and a common physiological role is suggested.