Cyclic 3',5'-nucleotide phosphodiesterase; cytochemical localization in rat renomedullary interstitial cells

The localization of cyclic 3', 5' -nucleotide phosphodiesterase activity in rat renal papillae was examined by utilizing cytochemical methods. Renal medullary interstitial cells had predictable phosphodiesterase activity predominantly on the cytoplasmic border of dilated cisternal membranes. Cells of the collecting tubule and loop of Henle contained diffuse reaction product. Capillaries had reaction product localized in pinocytic vesicles. Addition of theophylline resulted in no deposition of reaction product in interstitial cells and in cells of the collecting tubule and loop of Henle, suggesting an inhibition of phosphodiesterase activity. Since the membranes of dilated cisternae of renal medullary interstitial cells have been shown to be related to prostaglandin synthesis and probably to the anti-hypertensive function of these cells, the finding of phosphodiesterase activity on these membranes suggests a possible role of cyclic AMP in these two functions.