Rhodopsin in immature rod outer segments.
OBJECTIVE
To test the hypothesis that rhodopsin concentration is low in immature rat rod outer segments (ROS).


METHODS
Microspectrophotometry (MSP) was used to assess rhodopsin absorbances in localized regions of isolated ROS from dark-adapted 13-, 19-, and 34-day-old and adult rats. Photopigment was extracted from the retinas of paired eyes in dark-adapted and light-adapted rats. One retina of each pair was treated with 9-cis retinal before extraction of photopigment. Rhodopsin with native 11-cis retinal was extracted from the fellow retina.


RESULTS
By MSP, rhodopsin absorbance was low in the short ROS of 13-day-old rats. In 19-day-old rats with ROS lengths approximately equal to those of adults, absorbance was low at the tip, but at the base, it was equal to the high absorbance at both the tip and the base in adults. The 9-cis retinal did not add absorbance to the photopigment extracts of dark-adapted retinas at any age, but it did add absorbance to extracts of the light-adapted retinas at every age.


CONCLUSIONS
The MSP results show that the accumulation of rhodopsin in developing rat rods depends on increasing concentrations in localized regions. No evidence of apo-opsin is found in immature rat rods. Thus, in immature ROS regions, the low rhodopsin absorbances suggest that the amount of opsin is also low. Greater disk-to-disk spacing in immature ROS regions than in mature regions could account for these findings.
Dodge
J
J
Department of Biology, Florida State University, Tallahassee, USA.
Fulton
A B
AB
Parker
C
C
Hansen
R M
RM
Williams
T P
TP
D000375:Aging / Q000502:physiology; D000818:Animals; D003623:Dark Adaptation; D015591:Microspectrophotometry; D051381:Rats; D017207:Rats, Sprague-Dawley; D012243:Rhodopsin / Q000032:analysis*; D012374:Rod Cell Outer Segment / Q000737:chemistry* / Q000254:growth & development*; D017299:Rod Opsins / Q000032:analysis
D017299:Rod Opsins; D012243:Rhodopsin