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Fig. 4. Total and K-ras p21-GTP in mouse C10 and human HPL1D cells during culture growth and confluence. A and B, at left, the p21 standard. A, total K-ras p21 in C10 cells at 50 and 100% confluence; relative average densitometric scan values were 102 ± 30 and 389 ± 70, respectively. When normalized to total Erk1/2 protein (C), relative scan values were 64 ± 11 and 238 ± 21, respectively. B, activated K-ras p21-GTP in C10 cells; relative scan values were 14 ± 13 at 50% confluence and 130 ± 43 at 100% confluence. Normalized to total Erk1/2 protein (C), these were 8.5 ± 8.2 and 81 ± 20, respectively. C, the lysates used for the results shown in A and B were probed for Erk1/2 total protein, confirming approximately equal protein content. D, total K-ras p21 in HPL1D immortalized human lung cells at 50% confluency, relative scan value average 153 ± 46, and at 100% confluency, 564 ± 134. Normalized to {alpha}-tubulin protein (F), these values were 74 ± 23 and 279 ± 65, respectively. E, activated K-ras p21-GTP in HPL1D cells, relative scan values 68 ± 35 for 50% confluent and 596 ± 37 for 100% confluent. These values were 33 ± 7 and 283 ± 9 after normalization to {alpha}-tubulin (F). F, {alpha}-tubulin loading controls for the HPL1D cell extracts used for the data in D and E.