We have recently reported immunoassayable luteinizing hormone (LH) in several areas of the rat brain and conspicuously present in the hypothalamus. In this report, we focus on the presence of LH in the hypothalamus and its potential role in regulation of pituitary LH release. In adult female rats, examined during the course of the estrous cycle, a significant fall in hypothalamic LH coincides with the surge in pituitary and serum LH at the time of proestrus, signaling ovulation. Ovariectomized adult rats show no change in hypothalamic LH at a time when there is a dramatic rise in both anterior pituitary and serum LH. These data support the concept that hypothalamic LH is not of pituitary origin and that it may play a role in the short-loop negative feedback system controlling the surge in anterior pituitary LH release, an event initiating ovulation.

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This study describes the finding of an immunoassayable and bioassayable luteinizing hormone (LH) in the rat hypothalamus. Validation of the immunoassay for LH in hypothalamic extracts is presented.Chromatographic patterns of hypothalamic

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.

This laboratory has reported significant amounts of immunoreactive insulin (IRI) and glucagon (IRG) in pancreatic exocrine fluid of anesthetized dogs (Prinz, Kokal, Kirsteins, Smith, Lawrence and Paloyan 1978). In this study, human pancreatic exocrine fluid was examined and IRI and IRG were also found in high concentrations.