Nitrate-Induced Hypothyroidism is Associated with a Reduced Concentration of Growth Hormone-Releasing Factor in Hypothalamic Tissue of Rats

G. Jahreis; V. Hesse; W. Rohde; H. Prange; G. Zwacka

doi:10.1055/s-0029-1211049

Experimental and Clinical Endocrinology & Diabetes, Table of Contents

Exp Clin Endocrinol Diabetes 1991; 97(1): 109-112
DOI: 10.1055/s-0029-1211049

Short Communication

Nitrate-Induced Hypothyroidism is Associated with a Reduced Concentration of Growth Hormone-Releasing Factor in Hypothalamic Tissue of Rats

G. Jahreis¹ , V. Hesse¹ , W. Rohde³ , H. Prange² , G. Zwacka¹

¹Department of Paediatrics (Director: Prof. Dr. G. Zwacka), Friechich Schiller University, Jena/Germany
²Department of Pathology (Director: Prof. Dr. G. Waldmann), Friechich Schiller University, Jena/Germany
³Institute of Experimental Endocrinolog (Director: Prof. Dr. Dr. h. c. G. Dörner), Humboldt University, Berlin/Germany

Abstract

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Summary

Dietary nitrate significantly inhibits the growth of male and female rats. To test the possibility that the growth hormone-releasing factor (GRF) content in hypothalamic tissue is deranged under these conditions, male and female rats were fed a diet containing 3% KNO₃for 6 weeks, compared to a normal diet (4 × 5 animals). The food intake of rats fed nitrate was reduced significantly (23 and 28% resp.). Weight gain was also decreased by 35 and 41% in male and female rats. The mean Sm—C/IGF—I concentration was 1.61 and 1.03 rU/ml in male and female control rats, whereas the concentrations in nitrate-exposed rats were 0.92 and 0.64, respectively (P < 0.01). The GRF content of hypothalamic tissue also decreased significantly from 407 and 533 ng/g protein in controls to 174 and 229 in treated male and female rats. Nitrate exposure is characterized by hypothyroidism, food intake depression, low Sm—C/IGF—I concentrations in plasma and a decreased hypothalamic GRF content. Independent of the peripheral changes, the content of Sm—C/ IGF—I in the brain remains constant. The results of the study demonstrate that thyroid hormone deficiency leads to an inhibition of GH axis already at the hypothalamic level.

Key words

Nitrate - Hypothyroidism - Relapse - Growth hormone releasing factor - Somato-medin - C/Insulin-like growth factor

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