title: Thyroid autoregulation: evidence for an action of iodoarachidonates and iodide at the cell membrane level.
abstract: Iodolipids are the possible mediators of excess iodide in thyroid autoregulation. Previous work from our laboratory has shown that 14-iodo-15-hydroxy-5,8,11 eicosatrienoic acid (I-HO-A) and its omega lactone (IL-w) mimic the inhibitory action of excess iodide upon several parameters of thyroid metabolism. The present experiments were performed in order to study the mechanism of the inhibitory effect of I-HO-A and IL-w on 2-deoxy-D-glucose (DOG) and aminoisobutyric acid (AIB) uptake by calf slices. I-HO-A, IL-w and KI 0.1 mM caused a 33, 31 and 25% inhibition, respectively, of AIB uptake. The presence of 0.1 mM methimazole (MMI) only reversed the effect of KI. The transport of DOG was inhibited by both compounds: I-HO-A caused a 62% decrease, while IL-w produced a 64% inhibition; and MMI failed to relieve their action. On the contrary, the 33% inhibition caused by KI disappeared when MMI was present. Taking into account that AIB and DOG transport across the membrane requires energy, supplied by Na-K-ATPase, changes in its activity were studied. TSH (10 mU/ml) produced a 74% increase in the enzyme activity which was significantly blocked by KI (82%), I-HO-A (100%) and IL-w (100%). Basal enzyme activity was impaired by IL-w (33%), but not by KI. These results were correlated with the decrease of DOG uptake produced by 1 mM ouabain. Tissue specificity effect of iodoarachidonates was demonstrated by the absence of action on DOG transport in kidney and liver.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: División Bioquimica Nuclear, Comisión Nacional de Energía Atómica (CNEA), Buenos Aires, Argentina.
authors.forename: L
authors.initials: L
authors.lastname: Krawiec
authors.forename: H A
authors.initials: HA
authors.lastname: Chester
authors.forename: L V
authors.initials: LV
authors.lastname: Bocanera
authors.forename: L B
authors.initials: LB
authors.lastname: Pregliasco
authors.forename: G J
authors.initials: GJ
authors.lastname: Juvenal
authors.forename: M A
authors.initials: MA
authors.lastname: Pisarev
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D000621:Aminoisobutyric Acids / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D003847:Deoxyglucose / Q000378:metabolism; D006706:Homeostasis; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology; D008713:Methimazole / Q000494:pharmacology; D011193:Potassium Iodide / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013961:Thyroid Gland / Q000187:drug effects / Q000502:physiology*; D013972:Thyrotropin / Q000494:pharmacology
chemical_list: D000621:Aminoisobutyric Acids; D006893:Hydroxyeicosatetraenoic Acids; C055893:14-iodo-15-hydroxy-5,8,11-eicosatrienoic acid; D011193:Potassium Iodide; D008713:Methimazole; C030074:14-iodo-15-hydroxyeicosatrienoic acid, omega lactone; D013972:Thyrotropin; D003847:Deoxyglucose; D000254:Sodium-Potassium-Exchanging ATPase; D015126:8,11,14-Eicosatrienoic Acid