Ultrastructural Localization of Taurine Immunoreactivity in the Pineal Organ and Retina of the Pigeon

Abstract

While taurine is ubiquitous in animal tissues, some of the highest levels occur in the hypothalamus, pituitary gland, retina and pineal organ^{3, 11, 13}. This may indicate a role of taurine in processes that are more pronounced in neurosecretory and neurosensory cells than in other cell types. For example, taurine has been shown to interact with membrane phospholipids to alter their Ca²⁺ binding properties⁷, and may thus influence Ca²⁺-dependent processes such as ATPase ion pumps, ion channels flux, or Ca²⁺-activated events^{5, 6}, many of which contribute to neurosecretion and phototransduction. On the other hand, the large transient ionic fluxes associated with activity of pineal and retinal neurosensory/neurosecretory cells may also impose osmotic stresses that require use of taurine as an osmolyte; there is much evidence concerning a role for taurine in osmoregulation in tissues ranging from marine organisms, to the kidney and the brain^{5, 6}. The pineal organ contains many structures homologous to retinal photoreceptors. We hoped to gain information about the role of taurine in these tissues by examining and comparing the retinal and pineal distribution of endogenous taurine using immunocytochemistry.