Extrahypothalamic Brain Luteinizing Hormone:Characterization by Radioimmunoassay, Chromatography, Radioligand Assay and Bioassay

Abstract

We have recently reported that luteinizing hormone (LH) is present in the hypothalamus of rats. It has chromatographic and biologic characteristics similar to pituitary LH. In this report we focus on extrahypothalamic LH that is widely distributed in the rodent central nervous system. This material has a chromatographic profile similar to that of pituitary LH. Serial dilution of this material is parallel with dilutions of rat pituitary LH in the immunoassay. Brain extracts are active in the testis LH radioligand receptor assay and in the rat interstitial cell testosterone secretion bioassay. Prior incubation of extract with LH antibody significantly attenuates both of these activities. Thus, extrahypothalamic LH has immunologic, chromatographic, and biologic characteristics similar to hypothalamic and pituitary LH.

Immunocytochemical Distribution of Luteinizing Hormone in Rat Central Nervous System

“…Previously [19] we reported significant amounts of radioimmunoassayable LH in the forebrain, in the hypo thalamus, amygdala, septal area, preoptic area, thalamus, caudate, and hippocampus. Emanuele et al [10] similarly found immunoreactive LH in extrahypothalamic structures including the amygdala, thalamus, caudate, hippocampus, cerebellum, and cortex. However, in three brain areas, the hippocampus, cortex, and cerebellum, although detectable levels of LH were reported by radioimmunoassay, little or no LH immunoreactivity was visulized in the present study by immunocytochemistry.…”

“…40], thyroid-stimulating hor mone (TSH) [3,7,18,22,36,39,49,50], and prolactin [13-15, 48, 56], are present in brain. That this brain substance is similar or identical to pituitary LH is shown by gel chromatography [8,10,19], radioligand receptor, and bioassays [8,10]. Our laboratories, and others, have shown that immunoreactive LH appears to be located in distinct parts of the brain, because it is found by radioimmunoassay in the hypothalamus, amygdala, septal area, preoptic area, hippocampus, caudate nucleus, and thalamus [8,10,19].…”

“…That this brain substance is similar or identical to pituitary LH is shown by gel chromatography [8,10,19], radioligand receptor, and bioassays [8,10]. Our laboratories, and others, have shown that immunoreactive LH appears to be located in distinct parts of the brain, because it is found by radioimmunoassay in the hypothalamus, amygdala, septal area, preoptic area, hippocampus, caudate nucleus, and thalamus [8,10,19].The aim of this study was to use immunocytochemistry to determine more precisely the localization and distribu tion of the LH immunoreactivity in brain. In a previous study [19], we found LH-staining cells in the arcuate nu cleus of the hypothalamus, and delineated immunoreactive fibers in several forebrain areas.…”

Hypothalamic Luteinizing Hormone Increases Dramatically following Intracerebroventricular Injection of Colchicine

“…We have reported that LH is widely distributed in rat brain with highest levels found in hypothalamus, but LH is also found in the amygdala, caudate, cerebral cortex, hip pocampus, thalamus, cerebellum, and brain stem [6][7][8]. Both hypothalamic and extrahypothalamic LH have Sephadex chromatographic profiles identical to pituitary counterparts and are fully active in a radioreceptor assay system utilizing testes cell membranes.…”

“…Parlow. Details of the methodology used in this laboratory have been previously reported [8][9][10], Rat LH-RP-2 was used to develop the assay standard curves. Protein concentrations were de termined by the method of Waddell \ 19].…”