Depression of the electroretinogram in rats deficient in zinc and taurine during prenatal and postnatal life

Abstract

The objective of this study was to investigate whether zinc interacts with taurine to influence the development of the electroretinogram. Virgin female Sprague-Dawley rats were bred overnight and assigned to 1 of 4 treatments in a 2 × 2 factorial design with two levels of zinc (50 μg/g through gestation and 50 μg/g after parturition; 15 μg/g through gestation and 7.5 μg/g after parturition) and two levels of taurine (2 or 0 μmol/g). Guanidinoethyl sulfonate (10 g/L), a structural analogue of taurine, was added to the drinking water of the animals receiving 0 μmol/g taurine. At postnatal day 23, male pups ( n = 10) were weaned onto their respective diets. Dark-adapted electroretinograms were recorded as a function of stimulus intensity on 7 1/2–8 1/2-week-old anesthetized pups. Two-factor analysis of variance demonstrated no interaction between zinc and taurine for a- or b-wave amplitudes or latencies ( P < 0.05). Zinc and taurine deficiencies each independently depressed electroretinogram a-wave and b-wave amplitudes but not latencies. The amplitude of the b-wave was plotted as a function of log stimulus intensity, and an iterative curve-fitting procedure was used to determine the maximum response, slope, and half-saturation constant. No interaction was noted. A significant treatment effect on maximum response was demonstrated for zinc ( P = 0.0498) and taurine ( P = 0.0014). No treatment effects were evident for the half-saturation constant or slope. These findings indicate that zinc and taurine deficiencies are not synergistic in their depressing effects on the electroretinogram in this model.