[Role of adenosine in intraocular pressure]

Adenosine is thought to participate in the regulation of intraocular pressure since adenosine and several adenosine derivatives increase and/or decrease intraocular pressure. This article reviews the involvement of adenosine receptors in the regulation of intraocular pressure and the possible application of relatively selective adenosine A(2)-receptor agonists, 2-alkynyladenosine derivatives (2-AAs), as novel drugs for treatment of glaucoma. We found that some 2-AAs decreased intraocular pressure in normotensive rabbits. Moreover, these 2-AAs are also effective in the ocular hypertensive models induced by water-loading and alpha-chymotrypsin. In addition, the ocular hypotension induced by 2-(1-octyn-1-yl) derivative was inhibited by an adenosine A(2)-receptor antagonist 3,7-dimethyl-1-propargylxanthine, but not by an adenosine A(1) receptor antagonist 8-cyclopentyl-1,3-dipropyl xanthine. Moreover, the outflow facility was increased by the 2-(1-octyn-1-yl) derivative. These findings suggest that 2-AAs may affect intraocular pressure via adenosine A(2)-receptor, and 2-AAs-induced ocular hypotension is due to the increase in outflow facility. Some 2-AAs may be novel drugs against ocular hypertension and/or glaucoma, although additional studies are required to characterize the effects of 2-AAs on regulation of intraocular pressure in detail.