A radioautographic study on the incorporation of 14C-bupranolol (beta-blocking agent) into the rabbit eye

Localization of instilled 14C-bupranolol was studied in the rabbit eye by means of light microscopic radioautography. After the administration of 50 microliter of 14C-bupranolol into the eyes of two rabbits, both eyes were enucleated at intervals of 15 and 30 min respectively, and radioautographic procedures were carried out on cryostat sections by means of both dry-mounting and wet-mounting methods. Although with the former it was possible to demonstrate many radioautographic silver grains in the specimens, with the latter it was not possible to detect their localization. On the dry-mounting procedure, radioautographic grains were observed mainly in the epithelium of the ciliary body 15 and 30 min after the administration of 14C-bupranolol. The numbers of grains were counted on the 15 and 30 min specimens. They were decreased in the conjunctiva, and cornea 30 min after the administration. On the contrary, they were remarkably increased in the epithelium of the ciliary body. From these results it is concluded that the 14C-bupranolol first penetrates into the epithelium of the conjunctiva and cornea, then moves rapidly to the ciliary body, and that only very small amount of 14C-bupranolol is changed into the insoluble form. Also, these results suggest that bupranolol plays a role in the control of aqueous production in the ciliary processes.