Phospholipase D (PLD) is one of the intracellular signal transduction enzymes and plays an important role in a variety of cellular functions. We investigated the expression and cellular localization of the PLD isozyme PLD1 in the rodent retina. Western blot analysis showed the presence of PLD1 at the protein level in the rat, mouse and guinea pig retinas. PLD1 immunoreactivity was localized in all Muller cells. Thus, PLD1 protein appears to be important in the functions of these cells in the rodent retina. (C) 2001 Published by Elsevier Science B.V.