Figure 4

Effect of the ribozyme on the internalization of ¹²⁵I-labeled IGF-II (A). Ribozyme-treated or control cells were incubated in medium containing ¹²⁵I-labeled IGF-II with or without excess unlabeled IGF-II. Following incubation, cells were washed and cell-associated radioactivity was determined using a γ counter. Determination of binding (B) and endocytosis (C) of M6P-containing proteins in MCF-7 cells. The M6P-bearing enzyme β-glucuronidase was used as a probe. The M6P-inhibitable binding was measured by incubating saponin-peameabilized cells with β-glucuronidase in the presence or absence of M6P. The M6P-inhibitable uptake was determined by incubating cells with medium containing β-glucuronidase in the presence or absence of M6P. Following incubation, cells were washed extensively, and cell-associated β-glucuronidase was measured fluorometrically. Each point, the mean of three separate experiments (n = 3; ^*, p < 0.05; versus control).