en Pharmacology Pharmacology Original Research: Basic Science in Medicine Original Research: Basic Science in Medicine Sphingolipid metabolism was examined in guinea-pig airway smooth muscle cells stimulated by platelet-derived growth factor (PDGF) and 4β-phorbol 12- myristate 13-acetate (PMA), as mitogens and bradykinin (BK) as non-mitogen. Stimulation of the cells by PMA and PDGF for 60 min. at 37°C induced the following changes in sphingolipid metabolites: in cells prelabeled with PH] palmitate, a 1.2 fold increase in radio-labeled sphingosine, a concomitant 20% decrease in radio-labeled ceramide and no significant change in sphingomyelin level. Stimulation of the cells by BK induced no changes in sphingolipid levels at any time tested. This study demonstrates the existence of a "sphingomyelin cycle" in airway smooth muscle cells. Such sphingolipid cycles may function in a signal transduction pathway and in cellular proliferation. 57 63 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-498&slc_lang=en&sid=1 N MALEKI DIZAJI 20031947532846004923 20031947532846004923 Yes From the Department of Pharmacology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran A GARJANI 20031947532846004924 20031947532846004924 No From the Department of Pharmacology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran S PYNE 20031947532846004925 20031947532846004925 No the Department of Physiology and Pharmacology, University of Strathclyde, Glascow, U.K.