Cross competition for GPVI-Fc4 and CTRP-1 binding to fibrillar collagen. Plates were coated with collagen type I as described in “Materials and methods.” (Left) Each well was incubated with 0.3 μg ¹²⁵I-GPVI-Fc4/mL in the presence or absence of the indicated fold excess of unlabeled GPVI-Fc4 (♦) or CTRP-1 (•). (Right) Each well was incubated with 0.3 μg ¹²⁵I-CTRP-1/mL in the presence or absence of the indicated fold excess of unlabeled CTRP-1 (•) or GPVI-Fc4 (♦). The 100% values for ¹²⁵I-GPVI-Fc4 and ¹²⁵I-CTRP-1 binding in the absence of competitors were 2.87 ± 0.15 and 16.38 ± 2.11 ng bound/well (mean ± SD, n = 8 separate measurements), respectively. Each point represents the mean ± SD of 4 separate measurements from 2 separate experiments.