Maturational Patterns of Iodothyronine Phenolic and Tyrosyl Ring Deiodinase Activities in Rat Cerebrum, Cerebellum, and Hypothalamus

• Text
• PDF

Abstract

To explore the control of thyroid hormone metabolism in brain during maturation, we have measured iodothyronine deiodination in homogenates of rat cerebrum, cerebellum, and hypothalamus from 1 d postnatally through adulthood. Homogenates were incubated with 125I-l-thyroxine (T4) + [131I]3,5,3′-l-triiodothyronine (T3) + 100 mM dithiothreitol. Nonradioactive T4, T3, and 3,3′,5′-triiodothyronine (rT3) were included, as appropriate. The net production rate of [125I]T3 from T4 in 1-d cerebral homogenates was similar to the rate in adult cerebral homogenates (9.9±2.5[SEM]% vs. 8.9±1.2% T4 to T3 conversion in 2 h). Production of T3 was not detectable in 1-d cerebellar and hypothalamic homogenates. The net T3 production rate in adult cerebellar homogenates was twice as great as, and that in adult hypothalamic homogenates similar to, the rate in cerebral homogenates.

Authors

Michael M. Kaplan, Kimberlee A. Yaskoski