1. A luteinizing hormone-releasing hormone (LHRH)-like molecule produced by thymocytes is similar to hypothalamic LHRH in both bioactivity and antigenicity. 2. We determined whether this thymic LHRH is identical to or only homologous with hypothalamic LHRH by synthesizing and sequencing the cDNA of rat thymus LHRH. 3. The thymocyte and hypothalamic LHRH cDNAs are identical, indicating, that the amino acid sequences of LHRH produced in the hypothalamus and the immune system are also identical. 4. This is the first report showing conclusively that cell of the immune system transcribe the authentic mRNA for a hypothalamic releasing factor, LHRH.

To validate that growth hormone (GH) and growth hormone-releasing hormone (GHRH) can be produced by leukocytes, we have assessed the presence of GH and GHRH-related mRNA in leukocyte cultures by reverse transcription and the polymerase chain reaction. A sample of the polymerase chain reactions were size-fractionated by electrophoresis in a 0.8% agarose gel and examined with ultraviolet light after ethidium bromide staining. Single major DNA bands corresponding in length to the distance between the 5' ends of the two GH and GHRH specific primers, 603 base pairs and 260 base pairs, respectively, were obtained. The DNA bands hybridized specifically to GH- and GHRH-specific probes after Southern transfer to nitrocellulose. The identity of the GH polymerase chain reaction material was confirmed by restriction enzyme analysis. The results showed that GH and GHRH gene expression occurs in mononuclear leukocytes and support the idea that these neuroendocrine hormones may be common signal molecules between the immune and neuroendocrine systems.

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