Effects of osmotic dehydration on the nucleotides of isolated chromaffin granules: evaluation by 31p nuclear magnetic resonance.

The 31P nuclear magnetic resonance spectrum of chromaffin granules isolated from bovine adrenal medulla, when examined at 30 degrees C in 0.3 M sucrose, shows sharply defined gamma, alpha, and beta nucleotide resonances with linewidths of 141, 58 and 90 Hz respectively. These are essentially unchanged when examined at 4 degrees C. When the granules are resuspended in 1.6 M sucrose, the linewidths of 161, 117 and 162 Hz seen at 30 degrees C reversibly broaden to greater than 1000 Hz at 4 degrees C. Addition of quinacrine produces no discernable change in the nucleotide linewidths of either preparation. The broadening at high osmolarity and low temperature appears to be due to ATP:catecholamine complex formation rather than to increased viscosity. Since purification of chromaffin granules is often performed utilizing sucrose gradients, the present results raise the question of whether dehydration may alter the structure of the granule core.