Summary
In previous work changes of the thyrotropic secretion after administration of some
substances affecting the calcium content in the cytosol were demonstrated. The object
of the present investigation was to assess the hormonal response to the administration
of trifluoperazine, a psychopharmaceutical preparation, the main mechanism of its
action being the inactivation of the cytosol receptor for the calcium signal - calmodulin.
The poor utilization of intracellular calcium of the secretory cell is then the factor
which inhibits secretion proper. The thyrotropic secretory reserve (ΔTSH) was assessed
in the same subjects before and after trifluoperazine administration by the TRH test
as the difference of values at rest and TRH-stimulated TSH levels during the 20th,
30th, 40th and 60th minute following intravenous administration of 200 μg TRH. It
was revealed that this calmodulin antagonist administered for one week in amounts
of 6-12 mg per day by mouth significantly inhibits the secretory response of TSH to
TRH in healthy subjects during the 20th and 40th min. (P < 0.05). The reproducibility
of the TRH test repeated in a group of subjects not treated with trifluoperazine,
however, under equal conditions and after the same time intervals as in the experiment
with trifluoperazine was very satisfactory and thus physiological inhibition caused
by repeated TRH administration could be ruled out. The inhibition of the secretory
TSH response to TRH can be therefore considered the consequence of the direct effect
of trifluoperazine on the thyrotropic secretory mechanism.
Trifluoperazine significantly reduced serum calcium levels and raised phosphate levels,
while it did not affect the blood levels of magnesium.
Between the change of thyrotropic secretory response after trifluoperazine (Δ (ΔTSH))
and change of the serum calcium (ΔCa) a positive correlation was found during the
20th and 30th min. after TRH administration (P < 0.05 and P < 0.01, respectively).
No correlation was revealed between the Δ (ΔTSH) and change of the serum phosphate
level (ΔP).
Key-Words
Trifluoperazine
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Thyrotropic Secretory Reserve
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Calcium
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Phosphate
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Magnesium
