Quantitative histochemical studies of the hypothalamus: dehydrogenase enzymes following androgen sterilization

Abstract

Four enzymes, selected as representative of major metabolic pathways (malic dehydrogenase, of the citric acid cycle, lactic dehydrogenase, of glycolysis, glucose-6-phosphate dehydrogenase, of the pentose pathway and glutamic dehydrogenase, of glutamate metabolism), were measured by quantitative histochemical methods in individual hypothalamic nuclei of adult neonatally androgenized female rats. Malic dehydrogenase (MDH) was significantly reduced in nuclei of the anterior hypothalamus: the suprachiasmatic, supraoptic and anterior. Lactic dehydrogenase (LDH) increased significantly in the lateral preoptic area. Glucose-6-phosphate dehydrogenase G-6-PDH was also significantly elevated in anterior hypothalamic nuclei: medial preoptic, lateral preoptic, supraoptic and paraventricular. Glutamic dehydrogenase (GDH) was generally elevated throughout the hypothalamus with significant increases of activity occurring in the paraventricular, lateral ventromedial, arcuate, medial mamillary and posterior nuclei.

PIP: As part of a detailed analysis of the specific enzyme metabolism in individual hypothalamic nuclei during different endocrinological and behavioral states, quantitative distribution of a group of enzymes representative of major metabolic pathways was examined. Malic dehydrogenase (MDH), representative of the citric acid cycle, lactic dehydrogenase (LDH), of glycolysis, glutamic dehydrogenase (GDH), of glutamate metabolism, and glucoseo-6-phosphate dehydrogenase (G-6-PDH), of the pentose pathway, were measured in 11 hypothalamic nuclei, the cerebral cortex, and the cerebellum of adult female rats neonatally treated with testosterone propionate (TP). Several significant metabolic changes occurred in specific hypothalamic nuclei following neonatal TP (1 mg) treatment. MDH activity was significantly reduced in the suprachiasmatic (11%), supraoptic (13%), and anterior (9%) nuclei. No statistically significant changes occurred in nuclei of the middle or posterior hypothalamus. LDH was significantly elevated only in the lateral preoptic areas (23%). Several significant increases of G-6-PDH activity occurred in the following nuclei of the anterior hypothalamus: medial preoptic (32%), lateral preoptic (33%), supraoptic (13%), and paraventricular (23%). No statistically significant changes occurred in nuclei of the middle or posterior hypothalamus; these results were similar to those for MDH and LDH. GDH activity was generally elevated in all of the hypothalamic nuclei examined, except in the anterior nucleus. Significant increases of enzyme level were found in each of the major divisions of the hypothalamus. In the anterior hypothalamus, GDH activity in the paraventricular nucleus rose significantly (16%); in the middle hypothalamus, lateral ventromedial and arcuate nuclear levels were elevated (14 and 17%), and medial and posterior nuclear levels were higher than control values (32 and 36%) in the posterior hypothalamus.