125I-insulin receptor binding to cord blood erythrocytes of varying gestational age and comparison with adult values.

The measurement of 125I-insulin binding to erythrocytes from 34 samples of cord blood (% B/T = 11.2 +/- 3.8) showed statistically significant differences when compared to adult erythrocytes (% B/T = 6.6 +/- 1.7). Preterm erythrocytes (% B/T = 14.7 +/- 3.4) bound significantly more insulin when compared to term erythrocytes (% B/T = 10.1 +/- 3.2). The negative correlation (r = -0.613; P = 0.001) between insulin binding and gestational age indicates that the trend during the final trimester of gestation is toward the lower binding observed for adult cells. The major differences in binding between adult and term cord blood erythrocytes may be primarily attributed to differences in the number of binding sites per cell. Additionally, there are small differences in both affinity and number of sites per cell in preterm as compared to term and adult erythrocytes.