Gender and gonadal influences on ghrelin mRNA levels in rat stomach

Objective: The recently isolated endogenous GH secretagogue. named ghrelin, is a gastric peptide of 28 amino acids with an n-octanoylation in the seri ne 3 that confers the biological activity to this factor. Ghrelin has been shown to directly stimulate GH release in vivo and in vitro and to be invol ved in the regulation of gastric acid secretion and motility. In the presen t work we have studied gender and gonadal dependency of ghrelin mRNA expres sion in rat stomach. Design and Methods: We analysed ghrelin mRNA expression in rat stomach by N orthern blot analysis. We also examined the effect of gonadal steroid depri vation on ghrelin mRNA expression. Results and Conclusions: The results obtained showed clearly that ghrelin g astric mRNA expression increased with age in young rats (up to 90 days old) but exhibited no significant sex difference at each age tested. Ghrelin mR NA levels were lowest at postnatal day 9, reaching a stable level of expres sion at day 40 in both female and male rats, although the increase in femal e rats appears much more gradual than that in males. Moreover. neither ovar iectomy nor orchidectomy significantly modified ghrelin mRNA gastric levels in adult rats. In conclusion, these data indicate that ghrelin mRNA expres sion is associated with age and that a progressive increase is present from the perinatal period up to a stable level after puberty. Gonadal hormones did not alter ghrelin mRNA levels. Taken together, these data showed that g hrelin mRNA levels in young rats are age but not gender dependent, and are not influenced by gonadal steroids.