1,25-Dihydroxyvitamin D3 binding sites in the eye and associated tissues of the green lizard Anolis carolinensis

Abstract

Receptor autoradiography was used for the demonstration of specific binding of the tritiated steroid hormone 1,25-dihydroxyvitamin D3 in the eyes and associated tissues of Anolis carolinensis. A 100-fold excess of non-labelled 1,25-dihydroxyvitamin D3 abolished specific nuclear binding of tracer. Nuclear [3H]-1,25-dihydroxyvitamin D3 binding was present in all animals in the retina stratum ganglionare and stratum nuclear externum as well as in the cornea; however, binding was absent in the optic nerve, except in cells of the surrounding arachnoidea. Additional cranial tissues such as chondrocytes in the sclera, parasphenoid, skeletal muscle cells, and epithelial cells of the lacrimal and Harderian glands exhibited nuclear labelling. The results suggest that 1,25-dihydroxyvitamin D3 has genomic regulatory actions that involve cell proliferation, differentiation, and functions of certain cells of the eye and associated cranial tissues. The presence of vitamin D receptors in tissues of the eye and skeletal muscle in the reptile is in part different from that observed in mammals. In general, receptors for vitamin D and related target tissues appear to be even more extensive in lizards than has been observed in rodents, which may reflect a more extensive dependency of these tissues on solar environment and active seasonal and circadian regulation.

Nutrition research on calcium homeostasis. I. Lizards (with recommendations)

“…UVB is important for Ca homeostasis in lizards and for ultraviolet vision (Bidmon & Stumpf, 1995). The integument produces vitamin D 3 (cholecalciferol) when UVB light irradiates 7-dehydrocholesterol (provitamin D 3 ) (Bernard & Ullrey, 1995;Bidmon & Stumpf, 1995;Dierenfeld & Barker, 1995;Gascon et al, 1995;Holick et al, 1995;Frye, 1997;Laing & Fraser, 1999;Ullrey & Bernard, 1999 (Allen et al, 1993;Oftedal & Allen, 1996). A study comparing plasma vitamin D 3 of Komodo dragons Varanus komodoensis with and without daily exposure to UVB found that the plasma vitamin D 3 values in 75% of wild and captive Komodo dragons with daily exposure to UVB were 150-250 nmol/litre (Gillespie et al, 2000).…”

“…As in avian and mammalian species, the Green anole has high-affinity receptor sites for 1,25-dihydroxy-vitamin D 3 (1,25-D 3 or cholecalciferol) in chondrocytes (Bidmon & Stumpf, 1995). Vitamin D 3 is important for the growth and differentiation of cartilage, the elevation of plasma Ca and P (phosphorus), and it stimulates the active transport process of Ca and P from the small intestine to plasma (Holick et al, 1995).…”

“…Vitamin D 3 is important for the growth and differentiation of cartilage, the elevation of plasma Ca and P (phosphorus), and it stimulates the active transport process of Ca and P from the small intestine to plasma (Holick et al, 1995). Research in vitamin D 3 (1,25-D 3 ) metabolism in mammals also indicates it may be an immunomodulator (Lemire, 1992;Bidmon & Stumpf, 1995). Vitamin D may have a role in embryogenesis in some lizard species.…”

Nutrition research on calcium homeostasis. II. Freshwater turtles (with recommendations)

“…UVA can cause cellular death, cellular mutation and DNA damage but, in reptiles, UVA also stimulates feeding, sexual and territorial behaviours (Coohill, 1995;Boyer, 1996). UVB light is necessary for vitamin D biosynthesis and photoreception in reptiles (Bernard & Ullrey, 1995;Bidmon & Stumpf, 1995;Gascon et al, 1995;Holick et al, 1995;Kohen et al, 1995;Dickinson & Fa, 1997). However, the roles of UVA and UVB light in reptile physiology are still not fully understood and more research is needed on UV light and vitamin D biosynthesis (Bernard & Ullrey, 1995;Liesegang et al, 2001).…”

“…Vitamin D 3 is essential for the functioning of the immune system and the stimulation of the active-transport process of Ca from the small intestine into the plasma (Lemire, 1992;Bernard & Ullrey, 1995;Dierenfeld & Barker, 1995;Boyer, 1996). Cutaneous synthesis of vitamin D 3 occurs when the most appropriate air temperature and UVB light are available for a species (Bernard & Ullrey, 1995;Bidmon & Stumpf, 1995;Gascon et al, 1995;Holick et al, 1995;Kohen et al, 1995;Dickinson & Fa, 1997).…”