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Nocodazole inhibition of the vasopressin-induced water permeability increase in toad urinary bladder
Abstract:
Nocodazole is a synthetic antitumor drug that binds rapidly to tubulin. When this drug is applied to toad bladder prior to vasopressin stimulation it inhibits the vasopressin response. A maximum inhibition (68%) is reached with a dose level of 10 micrograms/ml applied one-half hour prior to vasopressin stimulation (20 mU/ml). This compares with an inhibition of 50% seen with a 3-h exposure of the tissue to colchicine (0.1 mM) prior to stimulation with vasopressin. Application of nocodazole (1 microgram/ml) 3 min after hormonal stimulation shows no inhibition of the response at one-half hour past stimulation. These data support the view that microtubules are involved in the vasopressin-induced increase in water permeability in toad bladder and also indicate that this involvement is limited to the period prior to or directly after stimulation.
Insights
Nocodazole, an antitumor drug, inhibits vasopressin-induced water permeability in toad bladders by targeting tubulin. This effect is most pronounced when applied before stimulation, suggesting microtubules are crucial for this response.
Area of Science:
- Cell Biology
- Pharmacology
- Physiology
Background:
- Vasopressin regulates water permeability in the toad bladder.
- Microtubules are intracellular structures with diverse cellular roles.
- The role of microtubules in hormone-induced water transport is not fully understood.
Purpose of the Study:
- To investigate the role of microtubules in vasopressin-induced water permeability in the toad bladder.
- To determine the effect of nocodazole, a tubulin-binding agent, on this physiological response.
Main Methods:
- Toad bladders were pre-treated with varying concentrations of nocodazole or colchicine.
- Tissues were subsequently stimulated with vasopressin.
- Water permeability was assessed by measuring water transport or related physiological parameters.
Main Results:
- Nocodazole significantly inhibited the vasopressin response in a dose-dependent manner, with maximum inhibition (68%) at 10 µg/ml applied 30 minutes prior to stimulation.
- Colchicine (0.1 mM) showed a 50% inhibition after 3 hours of pre-exposure.
- Nocodazole applied 3 minutes after vasopressin stimulation did not inhibit the response.
Conclusions:
- Microtubules play a critical role in the vasopressin-induced increase in water permeability in the toad bladder.
- The involvement of microtubules is primarily during the period preceding or immediately following hormonal stimulation.
