J. Biol. Chem., Vol. 261, Issue 19, 8589-8592, Jul, 1986
Insulin provokes a transient activation of phospholipase C in the rat epididymal fat pad
RV Farese, JY Kuo, JS Babischkin and JS Davis
Insulin is known to increase the de novo synthesis of inositol
phospholipids in rat epididymal fat pads. We presently examined the effects
of insulin on the hydrolysis of inositol phospholipids in this tissue.
Relatively small (30-40%) but significant increases in inositol phosphates
(mono-, di-, and tri-) were apparent within 30-60 s of insulin treatment in
fat pads (and adipocytes); thereafter, inositol phosphates returned to
control levels. These rapid insulin-induced increases in inositol
phosphates appeared to be due to phospholipase C- mediated hydrolysis of
inositol phospholipids, since there were associated transient decreases in
these lipids during 32P pulse-chase experiments. Increases in the synthesis
of inositol phospholipids were also apparent within a few minutes of
insulin treatment and persisted for at least 2 h. We conclude that, in the
rat epididymal fat pad, insulin has two phospholipid effects, viz. a
transient activation of phospholipase C, and a persistent increase in de
novo phospholipid synthesis.