Table IV.
Parameters of Dim Flash Responses in Ringer's and Prediction of Recovery Shift Due to Cyclase Activation
| Rod | τc′ | τ′nd | B Ca,rest | ΔT 0.8 | ΔT cyclase | ΔT residual | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| s | s | s | s | s | ||||||||
| a | 1.4 | 0.43 | 15 | 6.6 | 5.5 | 1.1 | ||||||
| b | 1.8 | 0.37 | 18 | 6.0 | 5.5 | 1.5 | ||||||
| c | 1.3 | 0.73 | 28 | 7.7 | 5.7 | 2.0 | ||||||
| d | 1.7 | 0.31 | 10 | 7.6 | 4.8 | 2.8 | ||||||
| e | 1.4 | 0.33 | 13 | 6.5 | 4.4 | 2.1 | ||||||
| f | 1.4 | 0.32 | 14 | 5.7 | 4.3 | 1.4 | ||||||
| g | 1.2 | 0.27 | 7 | 4.0 | 4.5 | −0.5 | ||||||
| h | 1.2 | 0.35 | 18 | 5.7 | 4.5 | 1.2 | ||||||
| i | 1.7 | 0.41 | 25 | 7.8* | 5.7 | 2.1 | ||||||
| j | 1.7 | 0.35 | 27 | 5.5* | 4.6 | 0.9 | ||||||
| 1.5 ± 0.2 | 0.39 ± 0.12 | 17.5 ± 7.2 | 6.2 ± 1.2 | 5.0 ± 0.6 | 1.5 ± 0.9 |
Column 1 identifies the rod. Columns 2–4 give the parameters of the model used to fit the low intensity responses in Ringer's, as illustrated in Figs. 11–13; the value of the amplification constant used is given in Table II, and in all cases the Hill coefficient was set to n H = 2. τc′ is the value of the larger time constant of the disc-associated reactions, and τ′nd the shorter time constant (Eq. 5). Column 4 gives the value of α′max = αmax/cG dark, the maximal rate of guanylyl cyclase activity divided by the concentration of cGMP in the dark (see ii). Column 5 gives the observed shift at the point of 80% recovery (20% response amplitude) between saturating responses obtained in choline and in Ringer's. Column 6 gives the shift predicted on the assumption that cyclase activation alone is responsible, calculated with Eq. 16. Column 7 gives the residual shift; i.e., the observed minus the predicted shift.
Rods i and j were recorded from in 0-Ca2+ choline, and for the reasons given in the notes to Table II, we were unable to measure ΔT 0.8 and have instead substituted ΔT 0.5.