The objective of this research was to indirectly determine the
existence of a possible retinal-endocrine pathway activated, or
Inhibited, by artificial fluorescent light as evidenced by it subsequent
effects on bone metabolism. Forty-eight male Long-Evans post-breeder
rats, half of which were bilaterally orbitally enucleated, were
used in this experiment. A 21-day pretreatment diet contained calcium
and phosphorus, each at a level of 0.2% of the diet, with no dietary
vitamin D. During the last seven days of this period the animals were
in complete darkness. For the 12-week experimental period, the diet
contained 0.6% calcium and 0.4% phosphorus, and oholecalciferol wets
administered the first day by intubation. During this time, four
groups of 12 animals each, half of which were bilaterally orbitally
enucleated, were exposed to either ultraviolet lights, cool green
lights, Vita-Lite (full spectrum) lamps, or kept in complete darkness
in specially constructed environmental boxes. On the first and last day
of the experimental period, the left femurs were x-rayed and blood was
sampled. The serum of the animals was analyzed for alkaline phosphatase,
total calcium and total phosphorus. Bone density was determined.
Femur ash was measured for total calcium and total phosphorus. Under
all lighting conditions, for both the sighted and enucleated rats, the
parameters measured in the serum declined. For serum alkaline phosphatase,
the sighted rats under the cool green lights had the least change;
the sighted in darkness had the greatest decline. The least change in
serum total calcium occurred for both the sighted and enucleated rats
under the cool green lights, whereas the greatest decline was for the
sighted rats under the Vita-Lite lamps and the enucleated under ultraviolet
lights. The sighted rats under the cool green lights had the
highest percent ash per gram of dry fat-free weight; the sighted under
the Vita-Lite lamps had the lowest. The highest ash calcium was in the
sighted rats under the cool green and the Vita-Lite lamps. By both
methods of bone density measurements, specific gravity and densitometry,
the sighted rats under the cool green lights had the greatest loss.
Overall there appeared to be more significant differences among the
sighted animals for the various lighting conditions than for the enucleated.
Also the enucleated rats had less extreme variations from the
mean than the sighted. The results of this study suggest that the light
mediated by the pbotoreceptors of the retina of the sighted rats produced
an effect on bone metabolism. / Graduation date: 1982
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27468 |
| Date | 07 January 1982 |
| Creators | McCarty, Ann Marie |
| Contributors | Miller, Lorraine T. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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