Vasoactive Intestinal Polypeptide in Rat Heart Atria: the Effect of
Hyperthyroidism
J. KUNCOVÁ, J. SLAVÍKOVÁ
Department of Physiology, Faculty of Medicine,
Charles University, Plzeň, Czech Republic
Received October 18, 1999
Accepted January 24, 2000
Summary
The effects of transient and sustained hyperthyroidism on
vasoactive intestinal polypeptide-like immunoreactivity
(VIP-LI) levels were studied in the heart atria of developing and adult rats.
Newborn rats were divided into 5 groups. Neo-T animals were treated with
thyroxine (T4) during postnatal days 1-8 and sacrificed at the age of 60 days.
Neo-S rats were treated with T4 during postnatal days 1-60 and sacrificed one
day later. Adult-1 and Adult-2 animals received T4 during days 52-60 and were
sacrificed 5-6 days and 1 day later, respectively. Control animals were injected
with saline. VIP-LI concentrations were determined in extracts from the left and
right atria separately. In Neo-S and Adult-2 rats, spontaneous heart rate, the
weight of both atria and total T4 serum levels were significantly enhanced,
while their body weight was decreased. The ratio atria weight to body weight was
significantly increased in all groups except for Adult-1 animals.
Hyperthyroidism led to a significant decrease in VIP-LI levels in both atria of
Neo-S and Neo-T rats. Hyperthyroidism induced in adult rats also decreased
VIP-LI levels in both atria. However, this change was only transient. In
conclusion, our data have provided new evidence that hyperthyroidism induced
during the early neonatal period interferes with the development of VIP-ergic
innervation in rat atria. The period of the first few postnatal days seems to be
essential for this effect, since VIP-LI concentrations in 60-day-old animals did
not significantly differ between Neo-S and Neo-T atria.
Key words
Vasoactive intestinal polypeptide ·
Hyperthyroidism · Heart ·
Rat · Development
Reprint requests
J. Kuncová,
Faculty of Medicine, Charles University, Lidická 1, 301 66 Plzeň, Czech
Republic. Fax: +420 19 521 943, e-mail: kuncova@lfp.cuni.cz
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