Distribution of LH-RH in subcellular fractions of the basomedial hypothalamus.
Subcellular fractionation of the mediobasal hypothalamus (MBH) and other brain structures was achieved by differential and sucrose gradient centrifugation. The fractions were monitored by measuring lactate dehydrogenase (LDH) activity (a marker for the soluble cytoplasmic fraction) and by electron microscopic examination. The luteinizing-hormone-releasing-hormone (LH-RH) content of the fractions was evaluated both by bioassay and radioimmunoassay. Significant amounts of LH-RH were found only in the MBH and in an anterobasal location corresponding to the organum vasculosum of the lamina terminalis. Within these areas, LH-RH activity was present in the first supernatant (homogenate with the exclusion of the nuclear pellet). Seventy percent of the LH-RH activity was recovered in the crude mitochondrial fraction. After further fractionation on a sucrose gradient, the distribution of LH-RH was parallel with that of LDH activity. Since LDH is predominantly located in the synaptosomal soluble fraction, it is concluded that the vast majority of LH-RH is contained within nerve endings. This finding is consistent with cyto-immunological data on the distribution of the neuropeptide in the rat hypothalamus.
D000818:Animals; D001681:Biological Assay; D002540:Cerebral Cortex / Q000032:analysis; D007987:Gonadotropin-Releasing Hormone / Q000032:analysis* / Q000276:immunology; D007031:Hypothalamus / Q000032:analysis*; D008297:Male; D008854:Microscopy, Electron; D009928:Organ Specificity; D011863:Radioimmunoassay; D051381:Rats; D013347:Subcellular Fractions / Q000032:analysis; D013574:Synaptosomes / Q000032:analysis / Q000648:ultrastructure
D007987:Gonadotropin-Releasing Hormone