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[Different susceptibilities to desensitization of three alpha 1-adrenoceptor subtypes induced by sustained
1Institute of Vascular Medicine, Third Hospital, Beijing Medical University.
Abstract:
cDNAs for the bovine alpha 1A-, hamster alpha 1B- and rat alpha 1D-adrenoceptors (AR) were transfected into human embryonic kidney 293 (HEK293) cells by calcium phosphate precipitation and stably expressed at high levels. The inositol phosphates (InsPs) accumulation was measured by the method of 3H-inositol incorporation and column chromatography. Susceptibilities to the desensitization of alpha 1-AR subtypes-mediated InsPs accumulation were determined in HEK 293 cells stimulated sustainedly by norepinephrine (NE). The NE-induced InsPs accumulation showed progressive decrease by NE pretreatment with increasing time of preincubation and concentration of NE in the cells transfected with all the alpha 1-AR subtypes. However, susceptibilities to the desensitization were different among the three subtypes. The desensitization of alpha 1A-AR took place earliest and needed lowest concentration of NE. The desensitization of alpha 1D-AR appeared to be the latest and needed hightest concentration of NE, while alpha 1B-AR stood in between.
Insights
Alpha 1-adrenoceptor (AR) subtypes exhibit varying sensitivities to norepinephrine-induced desensitization. Alpha 1A-AR desensitizes fastest, while alpha 1D-AR desensitizes slowest, impacting cellular signaling.
Area of Science:
- Pharmacology
- Molecular Biology
- Cell Biology
Context:
- Adrenoceptors (AR) play crucial roles in physiological processes.
- Understanding adrenoceptor subtype desensitization is key to receptor pharmacology.
- HEK293 cells provide a robust system for expressing and studying transfected receptors.
Purpose:
- To investigate and compare the desensitization kinetics of different alpha 1-adrenoceptor subtypes (alpha 1A, alpha 1B, and alpha 1D).
- To quantify the impact of norepinephrine (NE) concentration and preincubation time on receptor desensitization.
- To elucidate the differential signaling responses mediated by alpha 1-AR subtypes.
Summary:
- cDNAs for bovine alpha 1A-, hamster alpha 1B-, and rat alpha 1D-adrenoceptors were stably expressed in HEK293 cells.
- Norepinephrine-induced inositol phosphate (InsP) accumulation was measured to assess desensitization.
- All alpha 1-AR subtypes showed desensitization, but with distinct sensitivities: alpha 1A-AR desensitized earliest and at the lowest NE concentration, while alpha 1D-AR desensitized latest and at the highest NE concentration.
Impact:
- This study reveals differential desensitization profiles among alpha 1-AR subtypes, crucial for understanding their distinct physiological roles.
- Findings contribute to the development of subtype-selective drugs targeting adrenoceptor signaling pathways.
- Provides insights into the molecular mechanisms underlying adrenoceptor regulation and signaling.