Exogeneous diacylglycerols downregulate the activity of Na-K pump in Xenopus laevis oocytes

In this study, cell permeable diacyglycerols, sn-1,2-dioctanoglycerol (DiC8), and sn-1-oleoyl-2-acetylglycerol (OAG) were found to downregulate the activity of Na⁺-K⁺ pump in Xenopus laevis oocytes. Both DiC8 and OAG decreased the binding of ³H]ouabain to intact oocytes while phorbol esters did not appreciably influence the same. These diacylglycerols inhibited the amiloride-sensitive ²²Na⁺ influx and ouabain-sensitive ⁸⁸Rb⁺ uptake in the oocytes. Furthermore, DiC8 prevented the ²²Na⁺ efflux from the oocytes preloaded with ²²Na⁺. Addition of H-7 to DiC8- and OAG-treated oocytes stimulated the pump activity curtailed by the two latters. The impairment of Na⁺-K⁺ pump activity by diacylglycerols suggests that protein kinase C activators may stimulate endocytosis of membrane-coupled Na⁺-K⁺ ATPase.