Fig. 4.

Effect of extracellular RF level on RF uptake by pancreatic β-TC-6 cells. A: effect on RF uptake. β-TC-6 cells were maintained (72 h) in growth medium containing no added RF (deficient) or that supplemented with 100 μM unlabeled RF, followed by determination of initial rate of ³H-RF uptake. *P < 0.01. B: effect on level of expression of RFVT-1 protein. Western blotting was performed using equal amounts of total protein (60 μg) harvested from β-TC-6 cells maintained under RF-deficient and supplemented conditions and specific polyclonal antibodies. Expression of RFVT-1 was normalized relative to corresponding β-actin. Inset: results of a representative Western blot. **P < 0.05. C: effect on level of expression of RFVT-1 (and RFVT-2 and -3) mRNA. Total RNA was isolated from β-TC-6 cells maintained in RF-deficient and supplemented growth medium. Quantitative real-time PCR was performed using gene-specific primers. *P < 0.01. All results presented here are means ± SE of at least 3 independent experiments. D: effect on the level of expression of RFVT-1 heterogeneous nuclear RNA (hnRNA). RFVT-1 hnRNA level was determined as an index of transcriptional control using gene-specific primers. mRFVT-1, mouse RFVT-1. Values are means ± SE of 3 independent experiments. **P < 0.05.