Endocrine Abstracts

Arginine and other aminoacids have been reported to induce GH discharge, even if their site of action has not been clearly established. The aim of this study was to determine the effects of different culture media on GH secretion by pig pituitary cells. Pituitary cells from adult female pigs were cultured for 72 h in the following media: DMEM-F12 (Group A), DMEM-F12 SALTS (Group B) and DMEM-F12 ARGININE FREE (Group C), in standard culture condition (0-48 h: FCS 10%; 48-72 h: FCS 5%). The cells were cultured in 24 well-plates (200.000 cells/well), pre-treated with 10 μl of 0.1 milligrams per millilitre polilysine. After 48 h cells were treated with either h-leptin (10 ^-6M) or with arginine (10^-3M) for 24 h; at the end of culture, media were collected and assayed for GH concentration (ELISA) and for nitric oxide (NO) production (Griess Test). Each experiment was repeated at least 4 times with 8 replicates/treatment. Both leptin and arginine significantly (p<0.05) stimulated GH secretion in all groups. Leptin seemed to be effective in modulating NO production in B and C groups, whereas arginine induced a significant (p<0.05) rise in NO in A and C groups. These preliminary data clearly show that both leptin and arginine increase GH secretion, irrespective of culture condition. This is consistent with the observation that the pituitary is a site of marked expression of leptin receptor and that arginine-sensitive cells are distributed within all the anterior cell types. NO secretion appears to be involved in the control of GH release and it is well-known that leptin stimulates systemic NO production; however, our present findings indicate that the availability of nutrient substances is important to modulate cell responsiveness to leptin and also to arginine, which normally increases NO secretion.

This work was supported by a MIUR FIRB grant.