Water deprivation protects photoreceptors against light damage

Photoreceptor cell death after light-damage and during aging in rats is associated with the hormonal status of the animal, as well as other environmental and intrinsic factors. Restricted caloric intake extends the life of rodents and is usually accompanied by a reduction in water consumption. In this study, male and female rats were placed on restricted water intake for either 3 or 7 days to induce dehydration. Following exposure to damaging visible light, the retinas were evaluated for severity of damage and photoreceptor survival, heat shock (stress) protein (HSP) and total protein synthesis, and plasma arginine vasopressin (AVP) levels. Photoreceptor cells of 7-day, dehydrated male and female rats survived light-damage significantly better than those allowed water ad libitum; however, after 3 days of water restriction, only the male rats demonstrated protection from photodamage. Severity of photoreceptor damage could not be correlated with retinal HSP synthesis and content, although the latter was significantly reduced in dehydrated animals. Total retinal protein content and synthesis were unchanged by restricted water intake. AVP increased by 350% during the 7-day period of dehydration. Protection of photoreceptors from light-damage in this study may be correlated with osmotically stimulated changes in the retinas of dehydrated animals.