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

Abstract
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 signficant 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.