Variations among individual mice in binding of growth hormone and insulin to membranes from animals of different ages.

Binding of 125I-labeled insulin and growth hormone to membranes from liver and hearts of C57BL/6J mice was measured and the data analyzed by the graphical method of Scatchard. Animals were studied at ages 2, 10, 20, and 31 months; preparations from each animal were analyzed individually. There was no significant and progressive age-related difference in either dissociation constant or binding capacity for insulin in heart and liver, or for growth hormone in liver. Variations among individual animals were large; in some cases, the standard deviation exceeded the mean for a particular age group. We conclude that there are no large age related differences in binding of these anabolic hormones to the target tissues studied, and that any small changes would be masked by the large variations among individual animals.