Figure 4.

Ligand-binding specificity of VIP binding. Competition for binding of radioligand ¹²⁵I-VIP to membrane fractions of CAKI-1 human RCC was determined in the presence of increasing concentrations of VIP (○), JV-1–53 (▾), PG 97–269 (▿), JV-1–36 (■), JV-1–38 (♦), JV-1–42 (⋄), and MZ-5–156 (□). hGHRH(1–44)NH₂ (▴), hGHRH(1–29)NH₂, [His¹,Nle²⁷]hGHRH(1–32)NH₂, and glucagon as well as unrelated peptides, such as luteinizing hormone-releasing hormone, epidermal growth factor, [Tyr¹¹]somatostatin-14, [Tyr⁴]bombesin, and IGF-I, did not displace the radioligand (data not shown). One hundred percent specific binding is defined as the difference between binding in absence and in presence of 10⁻⁵ M VIP. Each data point represents mean of at least two experiments, done in duplicate or triplicate.