Lactate dehydrogenase isoenzymes of the hypothalamus, limbic structures, and the anterior pituitary during the estrous cycle.

Lactate dehydrogenase (LDH) and its isoenzyme (ISO) pattern were measured in the hypothalamus (HYP), amygdala (AMYG), hippocampus (HIP), cerebral cortex and anterior pituitary (PIT) of adult female rats sacrificed at different estrous cycle phases. The HYP, the AMYG and the PIT showed their maximal LDH values at proestrus and the lowest at diestrus. Those of the HIP showed the opposite pattern. The study of the ISO distribution pattern indicated that the cyclic variations of pituitary LDH activity were mainly due to changes of the ISO rich in A subunits, while in the B type they remained constant. By contrast, the cyclic changes of total LDH activity of all the brain structures studied were due to well balanced variations of both A and B subunits.