Cooperation of adipocytes and endothelial cells required for catecholamine stimulation of PGI2 production by rat adipose tissue.
Disturbances of prostaglandin I2 (PGI2, prostacyclin) production by adipose tissue contribute to the pathogenesis of diabetic ketoacidosis and may contribute to the pathogenesis of hypertension and vascular disease. We studied the cellular basis of PGI2 production in adipose tissue, measured as release of 6-keto-PGF1 alpha in response to epinephrine. Adipocytes did not produce PGI2 when nonfat cells were removed by repeated washing. The nonadipocyte cellular constituents of adipose tissue (nonfat cells) did not produce PGI2 in the absence of adipocytes. Both adipocytes and nonfat cells were required for PGI2 production in response to epinephrine. Adipocytes pretreated with 0.2 mM aspirin to inhibit PGH synthase nevertheless promoted PGI2 production when mixed with nonfat cells. Nonfat cells preincubated with aspirin did not produce PGI2 when mixed with adipocytes. The nonfat cells converted arachidonic acid to PGI2 but adipocytes did not. Epinephrine stimulated lipolysis and PGI2 production in a dose-dependent parallel manner, but the responses were distinct above 10(-6) M. Characterization of the nonfat cells by fractionation on a Percoll density gradient followed by measurement of angiotensin-converting enzyme activity and 6-keto-PGF1 alpha production indicated that the nonfat cells were predominantly vascular endothelial cells. We conclude that catecholamine-stimulated PGI2 production in adipose tissue results from the cooperation of adipocytes and vascular endothelial cells. The adipocytes provide arachidonic acid, which is converted to PGI2 by the vascular endothelial cells. Because adipose tissue is located near blood vessels throughout the body, adipocytes may be an important source of arachidonic acid for vascular endothelial cells in various circumstances in health and disease. Our findings raise the possibility that adipocytes may, under some circumstances, release arachidonic acid into the systemic circulation where it is used by vascular endothelial cells throughout the body to produce PGI2 and other eicosanoids.
Parker
J
J
Diabetes Unit, Massachusetts General Hospital, Boston 02114.
Lane
J
J
Axelrod
L
L
D015121:6-Ketoprostaglandin F1 alpha / Q000032:analysis / Q000096:biosynthesis; D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D002395:Catecholamines / Q000502:physiology*; D002450:Cell Communication / Q000187:drug effects; D002469:Cell Separation / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004837:Epinephrine / Q000494:pharmacology; D011464:Epoprostenol / Q000032:analysis / Q000096:biosynthesis*; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D001095:Arachidonic Acids; D002395:Catecholamines; D016718:Arachidonic Acid; D015121:6-Ketoprostaglandin F1 alpha; D011464:Epoprostenol; D001241:Aspirin; D004837:Epinephrine