title: Hormone selective lipase activation in the isolated rabbit heart.
abstract: The synthesis and release of PGs by the isolated perfused rabbit heart upon bradykinin stimulation results from lipase stimulation which liberates arachidonic acid for PG biosynthesis. The [14C]-labelled fatty acids, arachidonate, linoleate, and oleate, when infused into the heart preparation, were efficiently incorporated into the phospholipid pool in the heart mostly in the 2-position of phosphatidylcholine. On the other hand, [14C]-palmitate was esterified into both the 1- and the 2-position. Bradykinin released bioassayable PG when injected into the rabbit hearts, regardless of which fatty acid label was incorporated into the phospholipid pool. However, only [14C]-arachidonic acid (but not [14C]-linoleate, oleate or palmitate) was liberated from the variously labelled hearts upon hormone stimulation. This selective bradykinin effect on fatty acid release suggests that hormone stimulation either activates a specific lipase that distinguishes different fatty acids in the 2-position or activates lipase which is selectively compartmented with arachidonate-containing phospholipids. Ischemia, on the other hand, appeared to non-specifically stimulate tissue lipases, resulting in a non-selective release of oleic as well as arachidonic acid. A disproportionally large release of arachidonic acid was observed accompanying a relatively small PG (10:1 arachidonate: PG ratio) production during ischemia, as compared to bradykinin (3:1 ratio), suggesting distinct mechanisms for PG biosynthesis induced by bradykinin and ischemia.
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D001681:Biological Assay; D001920:Bradykinin / Q000494:pharmacology*; D003327:Coronary Disease / Q000378:metabolism; D006868:Hydrolysis; D007202:Indicators and Reagents; D008041:Linoleic Acids / Q000378:metabolism; D008049:Lipase / Q000378:metabolism*; D050356:Lipid Metabolism; D008297:Male; D009206:Myocardium / Q000201:enzymology* / Q000378:metabolism; D009829:Oleic Acids / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D011453:Prostaglandins / Q000096:biosynthesis; D011817:Rabbits
chemical_list: D001095:Arachidonic Acids; D007202:Indicators and Reagents; D008041:Linoleic Acids; D009829:Oleic Acids; D010713:Phosphatidylcholines; D010743:Phospholipids; D011453:Prostaglandins; D008049:Lipase; D001920:Bradykinin