Effect of known substrates of White on cyclic nucleotide transport
| Compound type . | Compound . | Concentration (μmol l–1) . | cGMP transport ratio (% of control) . | cAMP transport ratio (% of control) . |
|---|---|---|---|---|
| White/scarlet substrates | L-tryptophan | 2000 | 103±24 | |
| 1500 | 122±8 | |||
| 1000 | 100±8 | |||
| 500 | 95±24 | 135±25 | ||
| 250 | 104±23 | |||
| L-kynurenine | 2000 | 48±5** | 27±2** | |
| 1000 | 68±8 | 81±10 | ||
| 500 | 103±20 |
| Compound type . | Compound . | Concentration (μmol l–1) . | cGMP transport ratio (% of control) . | cAMP transport ratio (% of control) . |
|---|---|---|---|---|
| White/scarlet substrates | L-tryptophan | 2000 | 103±24 | |
| 1500 | 122±8 | |||
| 1000 | 100±8 | |||
| 500 | 95±24 | 135±25 | ||
| 250 | 104±23 | |||
| L-kynurenine | 2000 | 48±5** | 27±2** | |
| 1000 | 68±8 | 81±10 | ||
| 500 | 103±20 |
cGMP and/or cAMP transport assays were carried out on wild-type tubules in the absence (controls, 100%) or presence of known substrates of White/Scarlet. Percentage changes in the ratio of cGMP or cAMP transport compared to the controls are shown as mean ± s.e.m. (N⩾5). Significance was verified by Student's t-test compared with control (no added drugs), taking P<0.05 as the critical level. **P<0.01