RELEASE AND DISPOSITION OF H-3 NORADRENALINE IN THE SAPHENOUS-VEIN OF NEONATE AND ADULT DOGS

• Type: Article in International Scientific Journal
• Date: 1993

Authors

moura, d (Author) FMUP; Vaz Da Silva, M (Author) FMUP; AZEVEDO, I (Author) Other; BRANDAO, F (Author) Other; GUIMARAES, S (Author) Other

Journal

Title: Naunyn-Schmiedeberg's Archives of Pharmacology

Vol. 347

Pages: 186-191

ISSN: 0028-1298

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 11 Citations

Scopus - 11 Citations

Other information

Authenticus ID: P-001-NE2

Abstract (EN): Release of H-3-noradrenaline and formation of H-3-metabolites were studied in the saphenous vein of newborn (mean age, 18 h) and adult dogs. Vein strips were incubated with 0.23 mumol/I of H-3-noradrenaline during 1 h and washed out for 110 min; thereafter, the perifusion fluid was collected in 5-min samples. Electrical stimulation was applied at 120 min (I Hz, 2 ms, 100 V, for 5 min). In some experiments the tissues were preincubated with 1 mmol/I pargyline (to inhibit monoamine oxidase). In these experiments, 12 mumol/l cocaine (to inhibit uptake1), 41 mumol/I hydrocortisone (to reduce uptake2) and 50 mumol/l U-0521 (to inhibit COMT) were present during the perifusion. H-3-noradrenaline, H-3-DOPEG, H-3-NMN, H-3-DOMA and H-3-OMDA were separated by column chromatography. The noradrenaline content of the tissue was estimated by HPLC followed by electrochemical detection. A morphological study was also carried out by light and electron microscopy. The endogenous noradrenaline content of the saphenous vein was 4.3 times higher in adults than in neonates. The number of varicosities was similar in adults and newborns but the number of vesicles per varicosity profile was 5 times higher in adults. Hence, the endogenous noradrenaline content per vesicle was about the same in adults and newborns. The accumulation of H-3-noradrenaline per vesicle was about 5 times higher in newborns than in adults. On the other hand, the vein wall media of neonates was about 3 times thinner than that of adults. The evoked fractional release of tritium was about 10 times higher in neonates than in adults, whether the inactivation pathways were blocked or not. This difference in the evoked fractional release therefore cannot be ascribed to any difference in the efficacy of the inactivation pathways between neonates and adults. On the other hand, the difference also cannot be ascribed to a different alpha2-adrenoceptor-mediated inhibition of H-3-noradrenaline release since, as previously shown, this mechanism is as effective in newborns as in adults. It is concluded that the evoked fractional release of H-3-noradrenaline is higher in neonates than in adults because in neonates the majority of varicosities (and vesicles) is situated closer to the surface of the tissue such that both uptake from the surrounding media into the stores and release from the stores into the surrounding media become easier in the neonates.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 6