Iodine is given during the 7 to 10 days immediately preceding thyroid operation to decrease the vascularity of the gland, making it less friable and decreasing difficulties for the surgeon. The present work evaluated cholinesterase activity in rat thyroid glands on high iodine intake to establish a possible relationship between high iodine-induced vasoconstriction and parasympathetic activity. Male Wistar rats weighing 240-250g were given KIO3 (3mug/ml) as drinking water for 3 and 7 days; the control groups received tap water. At the end of the treatment period rats were sacrificed and their thyroid glands taken out, washed and weighed; the liver and the kidney were used as parameters of cholinesterase activity. Rats that received KIO3 for 7 days had a decreased thyroid gland weight compared to controls (p<0.05). However, no significant decrease in thyroid weight occurred after 3 days of treatment. At 3 days thyroid gland cholinesterase activity (nmol of acetylthiocholine hydrolysed/min.mg of protein) was 5.38±0.36 (mean±SD) in the control group (n=12) and 5.43±0.98 in the treated group (n=11) (NS). After 7 days of treatment cholinesterase activity was 5.42±0.27 in the control group (n=8) and 5.63±0.88 in the treated group (n=8) (NS). Our results suggest that the iodine-induced thyroid gland vasoconstriction is not due to changes in thyroid cholinesterase activity.
Thyroid gland; Cholinesterase activity; Iodine; Iodine excess
