A possible mechanism whereby parathyroid hormone stimulates phospholipid synthesis in canine renal tubules

: Incubation of canine renal cortical tubules with parathyroid hormone and [3H]glycerol stimulated incorporation of tracer into phosphatidylinositol 4-phosphate and decreased phosphatidic acid labelling but did not affect phosphatidylinositol, phosphatidylcholine/phosphatidylserine, phosphatidylethanolamine/phosphatidylglycerol, 1,2-diacyl- or triacylglycerol labelling. The hormone did not change the activity of glycerol 3-phosphate acyltransferase or of phosphatidate phosphohydrolase measured in tubule homogenates. However, parathyroid hormone induced a rapid increase in phosphatidylinositol kinase activity associated with a decrease in Km of the enzyme for ATP in homogenized tubules. These findings suggest a possible mechanism whereby parathyroid hormone increases phospholipid synthesis in the renal cortex.