ABSTRACT
Experimental evidence has suggested that the high endogenous levels of taurine found in the rat heart and retina are maintained to a large extent by transport processes out of the blood, rather than by endogenous biosynthesis. When these high levels are depleted, dysfunction ensues. In vitro studies have shown that beta-alanine is a good antagonist of these transport processes. The current studies were done to evaluate the feasibility of depleting heart and retinal taurine levels in vivo through treatment of adult rats either orally or with injections of beta-alanine. None of the treatments had significant effects on retinal taurine content; ventricular taurine was reduced in some situations, but the effects were not maintained, nor as large as with another transport antagonist. No functional changes were observed. Oral treatment with beta-alanine had fewer obvious side effects than injections, but all treated rats had body weights less than age-matched controls.
Subject(s)
Alanine/administration & dosage , DNA/metabolism , Heart/drug effects , Myocardium/metabolism , Retina/metabolism , Taurine/metabolism , beta-Alanine/administration & dosage , Administration, Oral , Animals , Injections, Intraperitoneal , Male , Rats , Rats, Inbred Strains , Retina/drug effectsABSTRACT
The number of axons in the optic nerve have been examined in rat pups raised by control or taurine-depleted mothers, at 21, 28 and 40 days after birth. Optic nerves from the mother rats were also studied. Taurine depletion of dams and some litters after weaning was achieved by in vivo treatment with guanidinoethyl sulfonate, an inhibitor of taurine transport. Retinal taurine content was reduced by this procedure and reductions in axon density (axons per area) were found in some groups. Comparison of axon densities obtained from light or electron micrographs suggested that taurine-deficient pups might have a higher proportion of small diameter fibres than controls, perhaps due to slowed growth and/or myelination. Reductions in the calculated total number of optic nerve fibres attained statistical significance consistently only in the treated dams. Ganglion cell degeneration may be direct or secondary to effects on taurine-sensitive elements at more distal retinal sites.
