Table 1.

Dimensions and visual pigment content of the photoreceptors

AnimalsRod density (no. per mm2)ROS diameter (μm)ROS length (μm)ROS volume (μm3)Packing densityVisual pigmentRod axial absorbancea
Amount per eye (nmol)Concentration (nmol/μm3)
P16 WT5.06  × 1051.26  ± 0.3214.04  ± 1.6917.51  ± 1.710.630.1720  ± 0.0300.00982  ± 0.00170.869
P12 WT7.16  × 1051.06  ± 0.266.42  ± 1.375.67  ± 1.500.620.0493  ± 0.0110.00869  ± 0.00190.351
P16 KO6.90  × 1051.11  ± 0.306.34  ± 1.496.14  ± 1.510.660.0563  ± 0.0100.00917  ± 0.00160.366
  • Rod density was derived by counting rows of rod nuclei per millimeter from 1 μm plastic sections. Rod outer segment width and length were measured from freshly dissociated photoreceptors, using a calibrated reticule. Those numbers were used to derive the total volume of the photoreceptors and their packing density (area of the mask minus the area of all the photoreceptors in the mask). Visual pigment concentration of the entire retina was derived from the color measured per mask area, a value that could then be used to determine the concentration of visual pigment per cubic micrometer and the resulting rod axial absorbance. Note that the values derived for the P12 and the P16 KO are virtually indistinguishable and significantly different from the P16 WT animals.

  • F1-a  Absorbance = ε ×c × l × 3/2; ε, extinction coefficient for mouse rhodopsin (4.2 × 104);c, concentration of rhodopsin (nmol/μm3); l, ROS length (cm), 3/2, orientation factor (Witkovsky et al., 1997).