Cyclic AMP and sodium transport. Quantitative and temporal relationships in toad urinary bladder
The Journal of Clinical Investigation
|September 1, 1973
Summary
Oxytocin increases toad bladder cAMP levels before affecting sodium transport (SCC). cAMP levels correlate with SCC, and sodium transport influences cAMP decay, suggesting a regulatory role.
Area of Science:
- Physiology
- Endocrinology
- Comparative Biology
Background:
- Oxytocin is a hormone known to influence various physiological processes.
- The urinary bladder of amphibians, like the toad Bufo marinus, is a model for studying ion transport.
- Cyclic adenosine monophosphate (cAMP) is a crucial second messenger in cellular signaling pathways.
Purpose of the Study:
- To investigate the effects of oxytocin on tissue cyclic adenosine monophosphate (cAMP) levels and short-circuit current (SCC) in the toad urinary bladder.
- To determine the quantitative relationship between oxytocin-induced cAMP changes and sodium transport.
- To explore the regulatory role of sodium transport on tissue cAMP levels.
Main Methods:
- Measurement of tissue cAMP content in response to oxytocin.
- Assessment of short-circuit current (SCC) across the toad urinary bladder.
- Analysis of the temporal relationship and dose-dependency between cAMP levels and SCC.
- Experimental manipulation of sodium influx to observe effects on cAMP decay.
Main Results:
- Oxytocin administration led to a doubling of tissue cAMP levels prior to any significant increase in SCC.
- A clear quantitative relationship was established between elevated cAMP levels and subsequent changes in SCC.
- A threshold concentration of cAMP was identified, necessary for observing an effect on sodium transport.
- The rate of cAMP increase was dependent on oxytocin concentration, affecting maximal cAMP levels.
- Reduced sodium influx delayed the decay of cAMP levels, indicating a sodium-regulatory mechanism.
Conclusions:
- Oxytocin stimulates cAMP production in the toad bladder, preceding the onset of enhanced sodium transport.
- cAMP acts as a mediator linking oxytocin stimulation to sodium transport regulation.
- Sodium transport itself appears to play a role in regulating tissue cAMP levels, suggesting a feedback mechanism.
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