Effect of protein depletion on the electric response of the retina in albino rats

Abstract

The limiting factor for seeing in dim light is the concentration ofrhodopsin in the retina. The formation of rhodopsin from opsin and the carotenoid retinene (vitamin A aldehyde) is the pre-requisite for the absorption of energy quanta. This in turn triggers electrical impulses which are propagated along the nervous pathways which connect the receptors with the brain. Deficiency of vitamin A leads, therefore, to hemeralopia. Wald (1955) has pointed out that the role played by opsin has been neglected in favour of its prosthetic group, vitamin A. Opsin may indeed be of equal importance, and a 'failure of opsin rather than vitamin A may be the predominant cause of night blindness'. It is therefore most probable that the lack of opsin would result in effects which are similar to those resulting from vitamin A deficiency.Since the impact of light quanta on the molecules of rhodopsin results in the elicitation of a nervous impulse, the measurement of the electrical response of the retina has proved to be an indicator of the rhodopsin concentration in the retina and, therefore, of the effects of deprivation of vitamin A. Moreover, the existence of a linear relation between the log threshold and the rhodopsin concentration could be demonstrated electroretinographically in albino rats (Dowling, 1960a, b;Dowling & Wald, 1960), and densitometrically in a colour-normal human observer and in a monochromat (Rushton, 1961a, b).In this paper the effect of protein depletion on the electrical response is investigated. It deals indirectly, therefore, with two further questions: whether the lack of protein interferes with the formation of opsin in the retina; and whether dietary deficiency of protein leads to changes in the electrical response of the retina similar to those found in vitamin A deficiency. Physiol. 172 27

A Ketogenic & Low-Protein Diet Slows Retinal Degeneration in rd10 Mice

“…Interestingly, it has been documented that protein deficiency and vitamin A deficiency decrease ERG amplitudes to a similar magnitude. 52 Because albumin is an important transporter for vitamin A, diminished ERG responses may correlate to a reduced bioavailability of vitamin A. 52 In summary, it remains unclear how protein deficiency impacted ERG responses.…”

“… 52 Because albumin is an important transporter for vitamin A, diminished ERG responses may correlate to a reduced bioavailability of vitamin A. 52 In summary, it remains unclear how protein deficiency impacted ERG responses. Additional experiments investigating the visual cycle and the functional bioefficacy of vitamin A may further our understanding.…”