SUMMARY BackgroundIt is controversial whether serum ghrelin concentration is altered in coeliac disease and whether this alteration is related to nutritional impairment or to inflammatory changes of duodenal mucosa.

It has been proposed recently that the melakonlin or 5-methoxy-N-acetyl-tryptamine pineal gland exerts an inhibitory influence (1). Support for this hypothesis comes from on the gonads and Ithat this inhibition is studies which have demonstrated that the mediated by a specific newrohumm called weightt of the pineal gland (2), and the activat Harvard Libraries on July 15, 2015 ebm.sagepub.com Downloaded from

The possible existence of a humoral communication between glial cells and LHRH-secreting neurons has been studied using the LHRH-secreting GT1-1 cell line and type 1 astrocytes. Two different designs have been adopted: 1) GT1-1 cells were coincubated with purified cultures of type 1 rat astrocytes, and 2) GT1-1 cells were exposed to the conditioned medium (CM) in which type 1 rat astrocytes had been grown for 24 h. LHRH was measured by RIA in the medium of the GT1-1 cell cultures at different time intervals. The data show that short periods (1, 3, and 6 h) of either coculture or exposure to previously frozen CM significantly increase the release of LHRH from the GT1-1 cells. However, more prolonged times of coculture (e.g. 2 and 5 days) or exposure to CM (e.g. 48 h) induce a significant decrease in the amount of LHRH in the medium. The stimulatory effect on LHRH release appears to be specific for type 1 astrocytes (either cortical or hypothalamic), because neither the CM of oligodendrocytes nor the CM of LNCaP cells (a cell line derived from a human prostatic cancer) possess stimulating activities. Heating the type 1 astrocyte-CM to 100 C for 10 min does not eliminate the ability of the CM to significantly increase the release of LHRH from GT1-1 cells at 1, 3, and 6 h. Because of the opposite effects encountered in the short and long term experiments, it was hypothesized that the CM might contain, in addition to LHRH-releasing principle(s), LHRH-degrading properties. Known amounts of standard LHRH were then added to type 1 astrocyte-CM, either untreated or submitted to heating at 100 C for 10 min. The amount of LHRH added to untreated CM decreases progressively; on the contrary, the amount of LHRH added to heated CM remains unchanged. These results confirm that one or more heat-sensitive enzymes able to degrade LHRH may be present in the type 1 astrocyte-CM. As previously mentioned, the experiments reported so far were performed using type 1 astrocyte-CM that had been kept frozen for various periods of time, before being tested for its LHRH-releasing activity. Surprisingly, fresh CM proves to be inactive, whereas heated CM is effective; this suggests that the factor involved might be activated by the two opposite experimental procedures.(ABSTRACT TRUNCATED AT 400 WORDS)

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