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An interaction of testosterone with cell membranes
Hormone and Metabolic Research = Hormon- Und Stoffwechselforschung = Hormones Et Metabolisme
|September 1, 1984
Summary
Testosterone rapidly increases liver glycogen phosphorylase activity in young chickens before protein synthesis, independent of nuclear interactions. This early effect involves decreased cyclic AMP (cAMP) levels, suggesting a novel non-genomic mechanism.
Area of Science:
- Endocrinology
- Biochemistry
- Molecular Biology
Background:
- Testosterone's genomic effects involve hormone-receptor complex interaction with the cell nucleus.
- Early, non-genomic effects of hormones are increasingly recognized but less understood.
- Investigating rapid testosterone actions in developing organisms provides insight into distinct signaling pathways.
Purpose of the Study:
- To explore the existence and nature of early testosterone effects in 3-day-old chickens, preceding nuclear-dependent actions.
- To determine the impact of testosterone on liver glycogen phosphorylase activity and cyclic AMP (cAMP) levels.
- To elucidate the potential mechanism of early testosterone action, distinguishing it from protein synthesis-dependent pathways.
Main Methods:
- Assaying liver glycogen phosphorylase activity in 3-day-old chickens following testosterone administration.
- Evaluating the effect of protein synthesis inhibitors (actinomycin D, cycloheximide) on testosterone-induced phosphorylase activation.
- Measuring intracellular cyclic AMP (cAMP) levels in response to testosterone and subsequent phosphorylase activation.
- Considering the role of intracellular calcium (Ca++) in mediating the observed effects.
Main Results:
- Testosterone administration led to a rapid increase in liver glycogen phosphorylase activity.
- This increase in enzyme activity occurred *before* any detectable activation of protein synthesis.
- The early activation of liver glycogen phosphorylase was not inhibited by actinomycin D or cycloheximide.
- Contrary to expectations, testosterone administration resulted in a significant depletion, not enhancement, of intracellular cAMP levels.
- The findings suggest a potential activation of phosphorylase kinase mediated by increased intracellular Ca++ concentration.
Conclusions:
- Testosterone exerts rapid, early effects in young chickens that are independent of protein synthesis and nuclear interactions.
- The observed depletion of cAMP and activation of liver glycogen phosphorylase suggest a non-genomic signaling pathway.
- A potential mechanism involving increased intracellular Ca++ leading to phosphorylase kinase activation is proposed for these early testosterone effects.