Alpha-2 receptor expression and rate constants for appearance and disappearance after 24 hr incubation with norepinephrine in the absence or presence of pertussis toxin
| Cell line | Appearance (r) | Disappearance (k) | Receptor expression (r/k) | Half-life | r 2 | n |
|---|---|---|---|---|---|---|
| %/hr | hr −1 | % | hr | |||
| HT29 | ||||||
| −Ptx | 20.5 ± 5.4 | 0.338 ± 0.082 | 61 | 2.1 | 0.96 | 3 |
| +Ptx | 3.6 ± 1.1* | 0.071 ± 0.017* | 51 | 9.8 | 0.97 | 3 |
| CHO-2A | ||||||
| −Ptx | 14.9 ± 7.2 | 0.270 ± 0.109 | 55 | 2.6 | 0.92 | 3 |
| +Ptx | 10.9 ± 6.5 | 0.201 ± 0.099 | 54 | 3.4 | 0.89 | 3 |
| CHO-2B | ||||||
| −Ptx | 16.6 ± 6.4 | 0.319 ± 0.103 | 52 | 2.2 | 0.94 | 4 |
| +Ptx | 11.3 ± 7.2 | 0.267 ± 0.129 | 42 | 2.6 | 0.89 | 4 |
For cells treated with pertussis toxin (Ptx), cells were first preincubated with 100 ng/ml pertussis toxin for 18 hr and incubated in the continued presence of pertussis toxin for the duration of the experiment. The data were fit to the repopulation equation to obtain values for r and k. Goodness-of-fit was estimated from the correlation coefficient (r 2) and from the runs test which was not significant (P > .05) in all cases. Extent of receptor expression is determined byr/k. * P < .05 as compared with −Ptx (Student’s t-test).