To establish changes in phototransduction in diabetes, the effects of high glucose on rhodopsin kinase (RK) and transducin (G(t)), as well as recoverin, were examined in the retina of STZ-induced diabetic rats. Diabetes was induced by single intraperitoneal injection of STZ (50mg/kg) to Sprague-Dawley (SD) rats and the animals were sacrificed after 6 weeks. Immunohistochemistry (IHC) and Western blot analysis were carried out using antibodies against RK and G(talpha) (alpha subunit of G(t)) in the STZ-induced diabetic retina and the control retina. The expression level of recoverin protein was also analysed. In the diabetic retina, while the expression of RK protein increased, that of G(talpha) and recoverin proteins decreased. RK immunoreactivity (IR) appeared generally in the retina, and its signal increased in the outer limiting membrane (OLM), some rod cells in the outer segment layer (OSL) and at the tip of the outer plexiform layer (OPL) in the diabetic retina. G(talpha)-IR also appeared in the OPL and in photoreceptor layer. In the diabetic retina, G(talpha)-IR significantly decreased in the OPL, indicating RK-IR increase. This study illustrates the alterations in RK, G(talpha) and recoverin in the diabetic retina that may induce dysfunctions in phototransduction even in early-stage diabetes.