Pigment granules: A calcium reservoir in the vertebrate eye

Abstract

Pigmented and non-pigmented ocular tissues from four categories of vertebrates (elasmobranchs, teleosts, amphibians and mammals) were analysed for the content and localization of calcium using thin section and bulk, wavelength and energy dispersive X-ray microanalysis and atomic absorption spectrophotometry. The pigment granules of the ciliary body, iris, retina pigment epithelium and choroidal melanocytes were found to contain 2-10 times more calcium than adjacent non-pigmented cytoplasm or cell organelles. Epidermal pigmented tissues (teleost and mammalian) analyzed for the presence of calcium, showed a slight elevation in the calcium content relative to similar non-pigmented cells and the surrounding cytoplasm, suggesting that pigment granules may be an intracellular calcium sink, especially in ocular tissues. © 1981 Academic Press Inc. (London) Limited.