Immunolocalization of calcitriol receptor, plasma membrane calcium pump and calbindin-D28k in the cornea and ciliary body of the rat eye.

Epitopes of the calcitriol receptor, the ATP-dependent plasma membrane calcium pump (PMCA) and the 28-kD vitamin-D-dependent Ca-binding protein (calbindin-D28k) were detected in sections of the albino rat eye using light microscopy and immunohistochemistry of paraffin-embedded tissues. Calcitriol receptor and calbindin-D28k epitopes were detected in both the inner and outer layers of the ciliary body epithelium. PMCA was present in both epithelial cell layers of the ciliary body but was most prominent in the inner layer. Corneal epithelium and endothelium also contained epitopes for calcitriol receptor, PMCA and calbindin-D28k. These Ca-regulatory proteins may play a role in the cellular physiology of the albino rat eye by maintaining appropriate intracellular and aqueous humor Ca concentrations.