Localization of d-myoinositol 1:2-cyclic phosphate 2-phosphohydrolase in rat kidney

Abstract

1. On subcellular fractionation of rat kidney homogenates by differential and density-gradient centrifugation, the bulk of the inositol 1:2-cyclic phosphate 2-phosphohydrolase activity remains with the alkaline phosphatase activity, suggesting localization in the brush borders of the proximal tubules. 2. Histochemical studies with a medium containing inositol 1:2-cyclic phosphate and Escherichia coli phosphomonoesterase show Gomori staining around the brush borders of the proximal tubules in the outer cortex only. 3. Serial sections across the kidney from cortex perimeter to papilla suggest that the inositol 1:2-cyclic phosphate 2-phosphohydrolase has a limited distribution along the proximal tubule of the nephron, probably being limited to the pars convoluta, whereas the alkaline phosphatase extends along the pars recta.

Phosphatidylinositol metabolism in cells receiving extracellular stimulation

“…A specific phosphodiesterase which causes its breakdown is fairly evenly distributed in tissues, except for disproportionate activity in brush borders of the epithelial cells in renal proximal tubules [79,89]. This exception may indicate a special function for the cyclic ester in these cells, but might also be an expression of biological economy as inositol is not rapidly synthesised by most tissues.…”

“…This exception may indicate a special function for the cyclic ester in these cells, but might also be an expression of biological economy as inositol is not rapidly synthesised by most tissues. Sequential action in kidney tubules of this phosphodiesterase, alkaline phosphatase [89] and an inositol-accumulating system [90] would prevent a loss into the urine of myoinosito1.…”

Phosphomonoesterase hydrolysis of polyphosphoinositides in rat kidney: Properties and subcellular localization of the enzyme system

“…The homogenate was centrifuged at 100OOg for 20min and the resulting pellet was washed three times with the 0.32M-sucrose solution. The microsomal fraction was then recovered by centrifuging the supernatant at 150000g for 1 h. The pellets were resuspended in a small volume of 0.25M-sucrose and subfractionated by the procedure of Clarke & Dawson (1972).…”