Influence of tissue freezing on the binding of 125I-sarcosine1, isoleucine8 angiotensin II to angiotensin II receptor subtypes in the rat

Xinyun Lu, W. Zhang, K. L. Grove, R. C. Speth

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Evaluation of angiotensin II (AII) receptor binding often necessitates freezing of the tissue of interest prior to assay of radioligand binding. This study evaluated the effects of freezing of various rat tissues at different rates on 125I-sarcosine1, isoleucine8 angiotensin II (125I-SI AII) binding to AII receptor subtypes. Slow freezing in a -20°C compartment significantly reduced 125I-SI AII binding to AT1 receptors in the adrenal (51%), epididymis (34%), and liver (22%). Binding of 125I-SI AII to the AT1 receptor in the brain was not significantly reduced. In the adrenal, both the Bmax and affinity of AT1 receptors were decreased by freezing. But in the epididymis, only the affinity of AT1 receptors was decreased. Binding of 125I-SI AII to AT2 receptors in the adrenal, epididymis, and brain was also not significantly reduced by freezing. Further evaluation of the mechanism of the reduction in 125I-SI AII binding to AT1 receptors in the adrenal indicated that both the receptor density and affinity for 125I-SI AII were decreased by freezing. Rapid freezing in a dry-ice bath caused even greater reductions in 125I-SI AII binding to AT1 receptors in the adrenal. Snap freezing in liquid nitrogen decreased 125I-SI AII binding in adrenals to a similar extent as did slow freezing. These results suggest that studies of AII receptor subtypes that involve freezing of the tissues underestimate the density and affinity of the AT1 receptor subtype.

Original languageEnglish (US)
Pages (from-to)83-90
Number of pages8
JournalJournal of Pharmacological and Toxicological Methods
Volume33
Issue number2
DOIs
StatePublished - Apr 1995
Externally publishedYes

Fingerprint

Angiotensin Receptors
Freezing
Angiotensin II
Rats
Tissue
Epididymis
Brain
Dry Ice
Radioligand Assay
Liquid nitrogen
Baths
Liver
Assays
Nitrogen

Keywords

  • AT
  • AT
  • Angiotensin II (AII) receptor binding
  • Freezing
  • I-sarcosine, isoleucine angiotensin II (I-SI AII)
  • Rat

ASJC Scopus subject areas

  • Toxicology
  • Pharmacology

Cite this

Influence of tissue freezing on the binding of 125I-sarcosine1, isoleucine8 angiotensin II to angiotensin II receptor subtypes in the rat. / Lu, Xinyun; Zhang, W.; Grove, K. L.; Speth, R. C.

In: Journal of Pharmacological and Toxicological Methods, Vol. 33, No. 2, 04.1995, p. 83-90.

Research output: Contribution to journalArticle

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abstract = "Evaluation of angiotensin II (AII) receptor binding often necessitates freezing of the tissue of interest prior to assay of radioligand binding. This study evaluated the effects of freezing of various rat tissues at different rates on 125I-sarcosine1, isoleucine8 angiotensin II (125I-SI AII) binding to AII receptor subtypes. Slow freezing in a -20°C compartment significantly reduced 125I-SI AII binding to AT1 receptors in the adrenal (51{\%}), epididymis (34{\%}), and liver (22{\%}). Binding of 125I-SI AII to the AT1 receptor in the brain was not significantly reduced. In the adrenal, both the Bmax and affinity of AT1 receptors were decreased by freezing. But in the epididymis, only the affinity of AT1 receptors was decreased. Binding of 125I-SI AII to AT2 receptors in the adrenal, epididymis, and brain was also not significantly reduced by freezing. Further evaluation of the mechanism of the reduction in 125I-SI AII binding to AT1 receptors in the adrenal indicated that both the receptor density and affinity for 125I-SI AII were decreased by freezing. Rapid freezing in a dry-ice bath caused even greater reductions in 125I-SI AII binding to AT1 receptors in the adrenal. Snap freezing in liquid nitrogen decreased 125I-SI AII binding in adrenals to a similar extent as did slow freezing. These results suggest that studies of AII receptor subtypes that involve freezing of the tissues underestimate the density and affinity of the AT1 receptor subtype.",
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AB - Evaluation of angiotensin II (AII) receptor binding often necessitates freezing of the tissue of interest prior to assay of radioligand binding. This study evaluated the effects of freezing of various rat tissues at different rates on 125I-sarcosine1, isoleucine8 angiotensin II (125I-SI AII) binding to AII receptor subtypes. Slow freezing in a -20°C compartment significantly reduced 125I-SI AII binding to AT1 receptors in the adrenal (51%), epididymis (34%), and liver (22%). Binding of 125I-SI AII to the AT1 receptor in the brain was not significantly reduced. In the adrenal, both the Bmax and affinity of AT1 receptors were decreased by freezing. But in the epididymis, only the affinity of AT1 receptors was decreased. Binding of 125I-SI AII to AT2 receptors in the adrenal, epididymis, and brain was also not significantly reduced by freezing. Further evaluation of the mechanism of the reduction in 125I-SI AII binding to AT1 receptors in the adrenal indicated that both the receptor density and affinity for 125I-SI AII were decreased by freezing. Rapid freezing in a dry-ice bath caused even greater reductions in 125I-SI AII binding to AT1 receptors in the adrenal. Snap freezing in liquid nitrogen decreased 125I-SI AII binding in adrenals to a similar extent as did slow freezing. These results suggest that studies of AII receptor subtypes that involve freezing of the tissues underestimate the density and affinity of the AT1 receptor subtype.

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