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Endogenous and Expressed Angiotensin II Receptors on Xenopus Oocytes
Author(s) -
Fluharty Steven J.,
Reagan Lawrence P.,
White Michael M.
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb11426.x
Subject(s) - xenopus , receptor , oocyte , endocrinology , medicine , biology , angiotensin ii , endogeny , population , follicular cell , follicular phase , microbiology and biotechnology , biochemistry , embryo , gene , environmental health
Intact Xenopus oocytes contain a homogeneous population of binding sites for the angiotensin II (Ang II) receptor antagonist 125 I‐[Sarc 1 ,Ile 8 ]‐Ang II ( 125 I‐SARILE). Binding of 125 I‐SARILE to intact oocytes was saturable and of high affinity with an apparent K D of 0.7 n M and maximal density of 0.12 fmol/oocyte. Binding of 125 I‐SARILE to oocytes also was specific for Ang II‐related peptides with a rank order potency of: [Sarc 1 ]‐Ang II > Ang II > Ang III Ang I. However, these endogenous binding sites were present only in follicle‐enclosed oocytes and within the follicular layer itself. On the other hand, injection of poly(A) + RNA isolated from murine N1E‐115 neuroblastoma cells into oocytes resulted in the appearance of 125 I‐SARILE binding sites even in defolliculated oocytes. These expressed receptors exhibited pharmacological properties similar to those endogenously present in the follicular layer, although their levels were much less. Collectively, these results suggest that endogenous Ang II receptors are present on Xenopus oocyte follicle cells, whereas Ang II receptors expressed from exogenous N1E‐115 RNA are found on the oocytes themselves. In addition, the high density of Ang II receptors on the follicle cells emphasizes the necessity for care in using Xenopus oocytes for the expression of receptors encoded by exogenous RNAs.