Angiotensin receptors in an Australian marsupial, the brushtail possum Trichosurus vulpecula

Journal Article · Mon Jan 01 00:00:00 EST 1990 · General and Comparative Endocrinology; (USA)

DOI:https://doi.org/10.1016/0016-6480(90)90212-5· OSTI ID:7105783

Sernia, C; Lello, P; Thomas, W G ^[1]

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1. Univ. of Queensland, St Lucia (Australia)

In this study, the binding properties of angiotensin receptors were examined in the liver, adrenal, brain, and vascular tissue of the brushtail possum, Trichosurus vulpecula. With 125I-Ile5-angiotensin II as the radioligand, the binding affinity (Ka) and receptor number (R0) were estimated for the liver (Ka = 3.60 +/- 0.31 liters/nmol; R0 = 23.8 +/- 1.30 pmol/g tissue; n = 8) and adrenal (Ka = 1.68 +/- 0.29 liters/nmol; R0 = 1.67 +/- 0.23 pmol/g tissue; n = 8). Specific binding was not found in any of seven areas of the possum brain (n = 6), whereas the expected binding was present in similar areas of the rat brain. Using angiotensin III or the antagonist Sar1-Ala8-angiotensin II as radioligands or changing the composition of the incubation buffer did not alter the outcome. Moreover, the intracerebroventricular injection of 1 and 5 nmol of angiotensin II did not elicit an increase in blood pressure which could be attributed to brain angiotensin II (AII) receptors. Ligand affinities of the adrenal and liver receptors were found to be in the following decreasing order: Val5-AII greater than Ile5-AII = Ile5-AIII greater than Sar1-Ala8-AII greater than Sar1-Gly8-AII greater than Sar1-Leu8-AII greater than Ile5-AI greater than hexapeptide greater than Phe3-Tyr8-AII. The cardiovascular AII receptor was investigated by generating dose-response curves of the pressor activity of Ile5-AII and six AII analogs infused intravenously. It was concluded that liver, adrenal, and vascular AII receptors in the marsupial possum have characteristics similar to those in eutherian mammals. However, the failure to find brain AII receptors raises the possibility that those functions mediated by such receptors in the eutherian brain are absent in the possum and perhaps other marsupials.

• OSTI ID: 7105783
• Journal Information: General and Comparative Endocrinology; (USA), Vol. 77:1; ISSN 0016-6480
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ANGIOTENSIN
RECEPTORS
BIOCHEMICAL REACTION KINETICS
ADRENAL GLANDS
AFFINITY
DOSE-RESPONSE RELATIONSHIPS
IODINE 125
LIGANDS
LIVER
MARSUPIALS
PEPTIDES
TRACER TECHNIQUES
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
CARDIOVASCULAR AGENTS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE GLANDS
GLANDS
GLOBULINS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
VASOCONSTRICTORS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques