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Immunoreactive Somatostatin and β-Endorphin Content in the Brain of Mature Rats after Neonatal Exposure to Propylthiouracil^*

NOBUMASA KATO, VALDINE C. SUNDMARK, LESTER VAN MIDDLESWORTH, VIKTOR HAVLICEK and HENRY G. FRIESEN

Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada R3E 0W3
the Department of Physiology and Biophysics, University of Tennessee Center for the Health Sciences (L.V.M.), Memphis, Tennessee38163

Address requests for reprints to: Dr. H. G. Friesen, Department of Physiology, University of Manitoba, 770 Bannatyne Avenue, Winnipeg, Manitoba, Canada R3E 0W3.

Abstract

The contents of immunoreactive somatostatin (IR-SRIF) and β-endorphin (IR-β-EP) in 12 brain regions were examined in rats exposed neonatally to propylthiouracil (PTU) through the mother's milk. Since the dose of PTU used in this study is lower than the usual dose employed to induce hypothyroidism, a milder form of neonatal hypothyroidism resulted. This conclusion is supported by the only mild subnormal growth of rats to adulthood and serum T₄ and T₃ concentrations in the normal range. Adult rats treated with PTU neonatally had significantly higher IR-SRIF contents in several brain regions compared to controls, whereas IR-β-EP levels were not significantly different (significant increase only in the thalamus) in most regions. The results indicate that even mild hypothyroidism during early postnatal development causes permanent impairment of brain function, which manifests itself in part by an altered brain content of IR-SRIF.

Footnotes

^* This work was supported in part by the MRC of Canada, USPHS Grant HD-07483-09, US Department of Energy Contract DEAS0576EVO1643, and USPHS Career Research Award 5K06-AM-00040.

Recipient of a MRC postdoctoral fellowship. Present address: Division of Metabolism, National Center for Nervous, Mental and Muscular Disorders, Kodaira, Tokyo 187, Japan.

Received February 8, 1982.