PubMed · 5802646
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M Ikeda, M Urakubo. 1969. Rod-cone interrelation.. https://doi.org/10.1364/josa.59.000217
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PURPOSE: To determine the roles of oxidation and glycolysis with aerobic and anaerobic lactate formation in the glucose metabolism of the cat outer retina in light and darkness. METHODS: Blood was collected from a choroidal vein and from an artery, and veno-arterial differences in lactate concentration (Lac(v-a) were determined at increasing light intensities. Blood also was sampled under conditions of darkness, light, and hyperoxia and were analyzed for oxygen, glucose, and lactate concentrations with or without blood flow determinations. RESULTS: When the dark-adapted eye was subjected to increasing light intensities, there was a reduction in the Lac(v-a), indicating reduced glycolysis in the outer part of the retina as the rods saturated. In darkness, the mean lactate formation per retina was 0.409 mumol/minute, oxygen consumption was 0.198 mumol/minute, and glucose consumption 0.236 mumol/minute. In light, the corresponding figures were 0.253, 0.166, and 0.123 mumol/minute. Hyperoxia reduced lactate formation and increased oxygen consumption in light and in darkness. CONCLUSIONS: Approximately 80% of the glucose consumed by the outer retina is used primarily in aerobic lactate formation. Because it is more efficient, oxidation of glucose still accounts for most of the energy production in light and in darkness. Light reduces oxidation as well as aerobic and anaerobic lactate formation.
The outer segments of vertebrate retinal photoreceptors undergo periodic shedding of membrane from their distal tips. This circadian rhythm of disk shedding persists with a period of about 24 h in the absence of external time cues. A circadian oscillator controlling photoreceptor disk shedding may exist in the eye, but in addition, the circadian clock in the hypothalamic suprachiasmatic nucleus (SCN) may also influence ocular rhythms including that of disk shedding. The tau mutation directly affects the SCN, and shortens the period of locomotor activity from 24 h in wild-type hamsters to 20 h in homozygous mutants. Here we show that homozygous tau-mutant hamsters in a 20-h light/dark cycle exhibit a 20-h oscillation in the rate of disk shedding, with peak phagosome numbers in the retinal pigmented epithelium occurring just after light onset. The numbers of phagosomes are significantly elevated from mid-dark levels prior to light onset, indicating that the disk shedding cycle anticipates dawn. Under conditions of constant darkness, the disk shedding rhythm in tau-mutant hamsters persists with a period of approximately 20 h. These results indicate that a rhythm of retinal photoreceptor outer segment disk shedding exists in the hamster eye, and that the period of this rhythm is shortened by the tau mutation.
To evaluate the effects of light and darkness on pyroglutamyl peptidase I activity (pGluPI) and its left-right distribution, pGluPI was measured bilaterally in the retina and hypothalamus under selected light-dark schedules. Rats under a 12 h light-dark cycle were divided into four experimental groups. After the end of the 12 h dark period, the animals were kept two additional hours in darkness (group 1), or light (group 2). After the end of the 12 h light period, the animals were kept two additional hours in darkness (group 3), or light (group 4). Experiments were done in light or darkness depending on the 2 h period. In the retina, a previous 12 h light period led to higher values of enzyme activity than dark periods. Left-right predominance, however, depended on the previous 2 h period: the light period led to left predominance, whereas right predominance was found after the 2 h dark period. In the hypothalamus, a left predominance was found only in group 3. These results demonstrate that environmental light conditions influence pGluPI activity in the rat retina and hypothalamus.