1,25-DIHYDROXYVITAMIN D-3 BINDING-SITES IN THE EYE AND ASSOCIATED TISSUES OF THE GREEN LIZARD ANOLIS-CAROLINENSIS

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