Target Cells of Vitamin D in the Vertebrate Retina

Abstract

Using PAP technique, cellular localization of vitamin D-dependent calcium-binding protein (D-CaBP) was investigated in vertebrate retina with monospecific antisera against chick duodenal D-CaBP. In the chick retina, the receptor cells were positive. In the inner nuclear layer, horizontal cells and some bipolar cells were also positive. Some amacrine cells as well as different levels of the inner plexiform layer were also positive for D-CaBP. A few interspersed ganglion cells were positive but their axons forming the optic tract were negative. Müller’s cells were negative. In 1-day-old chicks and 4-week-old rachitic chicks there was paucity and absence, respectively, of D-CaBP staining in horizontal cells. In the mouse, rat, and rabbit the receptors had only trace amounts of reaction product in their outer segment and pedicle. Horizontal cells were densely positive throughout their cellular body and processes. Some amacrine cells in the inner nuclear layer were positive. In the mouse and rat three horizontal levels of the outer plexiform layer were very prominent because of their dense staining for D-CaBP. Many ganglion cells were also positive along with their axons forming the optic nerve. In the rabbit, no positive layers were seen in the inner plexiform layer, and ganglion cells with their fibers were negative. In the frog retina there were smaller amounts of D-CaBP in the receptor cells and horizontal cells than that of the chick retina. Also, the fibers of the ganglionic cells were positive for D-CaBP. In all species studied, some amacrine cells were stained for D-CaBP. Because of its possible roles in membrane calcium transport and intracellular Ca⁺⁺ regulation, it has perhaps similar functions in these positive cells. The synthesis of D-CaBP is dependent upon vitamin D. These positive cells are thus target cells of vitamin D.

Comparative immunolocalization of the plasma membrane calcium pump and calbindin D28K in chicken retina during embryonic development

“…Our data on CaBP localization in chicken retina is quite similar to that found by Hamano et al (1990) and Ellis et al (1991). In contrast, Pasteels et al (1987) did not observe the presence of CaBP in the nerve fiber layer of the pigeon retina, nor did Schreiner et al (1985) in chicken retina. The prominent appearance of PMCA seems to coincide with the establishment of synapses, mainly in the inner plexiform layer.…”

“…The anti-CaBP antibody heavily stained the photoreceptor cells; the outer limiting mem-335 brane; regions within the outer nuclear layer including the synaptic pedicles of the receptor cells, and the outer plexiform layer. A few cells intensely stained in the inner component of the inner nuclear layer, presumably amacrine cells (Schreiner et al, 1985) and in the inner plexiform layer. Some ganglion cells and processes in the nerve fiber layer were also CaBP positive.…”

“…Schreiner et al (1985) had observed that the presence of CaBP on horizontal cells of chicken retina is dependent on nutritional vitamin D status. Overall, immunostaining of CaBP in chicks fed a rachitogenic diet was lower than that of chicks of the same age fed a normal diet.…”

“…The exact cellular location of these proteins varies among species and among specific cell types. Identified within one or more of these cells are calmodulin (Pochet et al, 1991), calbindin (Schreiner et al, 1985;Pochet et al, 1991;Pasteels et al, 1987;Veccino et al, 1993;Papzafiri et al, 1995;Yan, 1997;Haley et al, 1995;Dalil-Thiney et al, 1994), calretinin (Rogers, 1989;Pasteels et al, 1990;Papzafiri et al, 1995;Völgyi et al, 1997), parvalbumin (Uesugi et al, 1992;Yan, 1997), hippocalcin (Bastianelli et al, 1995) and caldendrin (Menger et al, 1999). The function of many of these proteins, except the ubiquitous calmodulin, is the subject of speculation and, in certain cases, controversial.…”

Calretinin: a gene for a novel calcium-binding protein expressed principally in neurons [published erratum appears in J Cell Biol 1990 May;110(5):1845]

“…But elsewhere in the brain, calbindin and parvalbumin immunoreactivities are mostly in separate neurons (9,11,24). Both are also present in rat retina (17,50), and calbindin immunoreactivity is present in chick retina (25,53,58).The function of these proteins in neurons is unknown. An initial suggestion that parvalbumin was colocalized with GABA (15) has not been generally confirmed by more extensive surveys (13, 18).…”