1,2-Diacylglycerols and phorbol esters stimulate phosphatidylcholine metabolism in GH3 pituitary cells. Evidence for separate mechanisms of action Academic Article uri icon

Overview

MeSH Major

  • Diglycerides
  • Glycerides
  • Phorbol Esters
  • Phosphatidylcholines
  • Pituitary Neoplasms

abstract

  • Phorbol esters have been shown to cause degradation and synthesis of phosphatidylcholine. The present studies measure effects of another class of protein kinase C activators, the 1,2-diacylglycerols, on phosphatidylcholine metabolism using GH3 rat pituitary cells. 1,2-Dioctanoylglycerol (diC8, 200 micrograms/ml) reduced phosphatidylcholine levels to 95 and 70% of control by 5 min and 1 h, respectively, in cells labeled to equilibrium with [3H]choline. Concomitantly, lysophosphatidylcholine increased 3.5-fold by 15 min and remained elevated for 1 h. Glycerol 3-phosphocholine, the product of sequential deacylation of phosphatidylcholine, increased 5-fold in the medium over 1 h. DiC8 also increased the levels of unesterified arachidonic and stearic acids. Arachidonic acid was preferentially released from the 2-position of phosphatidylcholine to form lysophosphatidylcholine. These results suggest that diC8 stimulates a phospholipase A2. 1-Oleoyl-2-acetylglycerol produced similar effects. In contrast, phorbol esters failed to enhance degradation in these cells. 1,2-Diacylglycerols and phorbol esters, however, stimulated phosphatidylcholine synthesis via the CDP-choline pathway. This was measured as concentration-dependent incorporation of 32Pi and [3H]choline into phosphatidylcholine in short-term labeling studies. The effects of maximal concentrations of diC8 and the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate, were additive. Furthermore, in cells down-modulated for phorbol ester action, diC8-induced degradation and synthesis were unchanged. These studies demonstrate that phorbol esters and 1,2-diacylglycerols have different effects on phosphatidylcholine metabolism and suggest that 1,2-diacylglycerols may stimulate phosphatidylcholine metabolism via a pathway independent of the protein kinase C which mediates phorbol ester action. This represents the first description of a biochemical pathway activated by 1,2-diacylglycerols and not by phorbol esters.

publication date

  • January 1987

Research

keywords

  • Academic Article

Identity

Language

  • eng

PubMed ID

  • 3597411

Additional Document Info

start page

  • 9204

end page

  • 10

volume

  • 262

number

  • 19