In this study, we investigated the differences in
calbindin D-28k (CB),
calretinin, (CR) and
parvalbumin (PV) immunoreactivity in the hippocampus of Zucker diabetic fatty (ZDF) rats and Zucker lean control (ZLC) rats. In addition, we observed the effects of
hypothyroidism on the levels of immunoreactivity of these
proteins in ZDF rats. For this study, 7-week-old ZDF rats were used, and
methimazole treatment was continued for 5 weeks to induce
hypothyroidism. The animals were sacrificed at 12 weeks of age. ZDF rats showed increased
blood glucose levels compared to those in ZLC rats.
Methimazole intervention significantly reduced total and free T3 levels, and it ameliorated the increase of
blood glucose levels in ZDF rats. In ZLC rats, CB, CR, and PV immunoreactivity was detected in regions of the hippocampus proper. In vehicle-treated ZDF rats, CB, CR, and PV immunoreactivity was significantly decreased in the hippocampus. However, in the
methimazole-treated rats, CB, CR, and PV immunoreactivity was significantly increased compared to that in the vehicle-treated rats. These results suggest that
hypothyroidism ameliorated the diabetes-induced reduction of CB, CR, and PV immunoreactivity in the hippocampus.