POSTNATAL-DEVELOPMENT OF VASCULAR BETA-ADRENOCEPTOR-MEDIATED RESPONSES AND THE INCREASE IN THE ADRENALINE CONTENT OF THE ADRENAL-GLAND HAVE A PARALLEL TIME-COURSE

• Type: Article in International Scientific Journal
• Date: 1994

Authors

PAIVA, MQ (Author) Other; moura, d (Author) FMUP; Vaz Da Silva, M (Author) FMUP; GUIMARAES, S (Author) Other

Journal

Title: Naunyn-Schmiedeberg's Archives of Pharmacology

Vol. 350

Pages: 28-33

ISSN: 0028-1298

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 4 Citations

Other information

Authenticus ID: P-001-JXP

Abstract (EN): The present study was undertaken to analyse the relationship between postnatal development of vascular beta(2)-adrenoceptor-mediated responses and the content of adrenaline in the adrenal gland and its concentration in plasma. Dog saphenous vein tissue from newborn, two-weeks old and adult animals were either preloaded with H-3-noradrenaline (or H-3-adrenaline) to study prejunctional beta-adrenoceptor-mediated effects or mounted in organ baths to determine isoprenaline-induced relaxation of preparations contracted by phenylephrine to about 65% of the maximum. The adrenal glands and samples of blood from the same animals were taken for estimation of adrenaline and noradrenaline. At birth, there were no beta-adrenoceptor-mediated effects pre- or postjunctionally. At two weeks, while the results at the prejunctional level were not significantly different from those obtained in newborns, at the postjunctional level there was a relaxant response to isoprenaline, which antagonised about 35% of the previous contraction to 1.75 mu mol l(-1) phenylephrine. In adults, isoprenaline (50nmol . l(-)1) increased by 24% tritium overflow evoked by electrical stimulation of tissues preloaded with H-3-noradrenaline but not that of tissues preloaded with H-3-adrenaline. On the other hand, propranolol (1 mu mol . l(-1)) reduced by 21% the overflow of tritium evoked by electrical stimulation of tissues preloaded with H-3-adrenaline but not that of tissues preloaded with H-3-noradrenaline; postjunctionally, the maximal response to isoprenaline antagonised 70% of the previous contraction to 1.75 mu mol . l(-1) phenylephrine. At birth the catecholamine content of the adrenals was relatively low (2.9 mu mol . g(-1)) and the adrenaline/noradrenaline ratio was 0.26; two weeks later, the catecholamine content was 14.5 mu mol . g(-1) and the adrenaline/noradrenaline ratio was 0.74; in adults, the catecholamine content was 24.5 mu mol . g(-)1 and the adrenaline/noradrenaline ratio was 2.3. In plasma, the highest concentration of adrenaline was observed at birth (11.8 nmol . l(-1)); two weeks later it was 5.5 nmol . l(-1) and in adulthood it fell to 3.1 nmol . l(-1). On the basis of these results, it is concluded that some link between the postnatal increase in adrenaline adrenal content and the development of beta 2(-)adrenoceptor-mediated pre- and postjunctional effects may exist. Additionally it is suggested that circulating adrenaline may trigger the development of beta(2)-adrenoceptor-mediated responses as well as some hypertensive states occurring as a consequence of an overreactivity of the sympathoadrenal system.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 6