The involvement of Rho-kinase in P2Y-receptor induced contraction of isolated rat renal glomeruli was investigated. The contraction effects have been investigated based on changes in the intracapillary volume of isolated glomeruli. ATP was found to induce time- and concentration-dependent contraction of isolated glomeruli. Other tested nucleotides (ADP, UTP) and ATP analogues (beta,gamma-methylene-ATP, 2-methylothio-ATP) contracted glomeruli in similar magnitude whereas AMP had no effect. Furthermore, the contractive effect of ATP was prevented in the presence of an antagonist of P2Y-receptors, reactive blue 2. However, a selective antagonist of A1-receptors, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), had no effect. Contraction induced by ATP, ADP, and UTP, in contrast to 2-methylothio-ATP and beta,gamma-methylene-ATP, was prevented in the presence of Rho-kinase's inhibitor, (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632). These findings suggest the involvement of Rho-kinase pathways in P2Y-induced contraction of isolated glomeruli. (C) 2003 Elsevier Science (USA). All rights reserved.