~ s T ~ ELSEVIER Regulatory Peptides 63 (1996) 73-78 REGULATORY PEPTIDES LHRH and somatostatin effects on the cell proliferation of the gastric epithelium of suckling and weaning rats Patr¢cia Gama, Eliana Parisi Alvares * lnstituto de Ci~ncias Biom~dicas, Departamento de Histologia e Embriologia. Universidade de S~to Paulo, At. Lineu Prestes 1524. S~o Paulo 05508-900 SP, Brazil Received 13 November1995; revised2 January 1996; accepted7 January 1996 Abstract The aim of this study was to investigate the effects of LHRH and somatostatin on the cell proliferation of the gastric epithelium of suckling and weaning rats after fasting treatment. Previous studies on the cell proliferation of the gastric epithelium have shown that fasting stimulates this process in suckling, but not in weaning and adult rats. As milk is the most important source of nutrients and hormones during the suckling phase, and luteinizing hormone-releasing hormone (LHRH) and somatostatin are found in milk, their possible inhibitory roles on the gastric epithelium were investigated. Metaphasic index was achieved by vincristine blockade in 18- and 22-day-old treated and non-treated rats. The results showed that at 18 days, both hormones inhibited the enhanced proliferation activity due to fasting treatment, while at 22 days, no effect was detected. Therefore, LHRH and somatostatin were considered to have inhibitory roles on the cell proliferation of the gastric epithelium in suckling rats only. Keywords: Stomach; Postnatal development;Milk hormone; Mitosis 1. Introduction The epithelia of the gastrointestinal tract are continu- ously being renewed and this process is assured by cell proliferation, migration, differentiation and death. During postnatal development, the mechanisms which control these processes may involve different factors, such as hormone levels, feeding pattern and its metabolic associated changes [1,2]. Thus, the normal mucosa involves a balance of tbrces which act on its destruction and those which aim to keep it [3]. During the milk-intake period, it was shown that fasting treatment enhances cell proliferation in the stomach epithe- lium of the rat [4,5], in contrast to the inhibitory effect previously observed in adult animals [6,7]. Food transition is thus parallel to the different proliferative responses. Moreover, the rise in hormone levels which are thought to have regulatory roles on the gastrointestinal tract [8-11] occurs by the end of the third postnatal week, that is weaning time [12-14]. During the suckling period, milk can supply lots of hormones and growth factors [15,16], such as glucocorticoids, thyroxine, bombesin and EGF, which can control the development of the pup [ 17-19]. The luteinizing hormone-releasing hormone (LHRH) is a milk-borne hormone which has a modulatory action on its own number of receptors in the ovary and pituitary in the infantile rat [20]. It is inhibitory for the cell prolifera- tion of tumors [21,22], but it can also lead to a proliferative stimulus in the rat thymus [23,24]. Somatostatin has been characterized as a growth hormone inhibitor [25] eliciting an antitrophic effect in the gastric epithelium of young rats [26] and it is also present in milk [27]. Thus, as LHRH and somatostatin are released in milk they could have an inhibitory influence on the cell proliferation of the gastric epithelium of the suckling rat, so that during the fasting state, the proliferation indices are increased. Therefore, the present study was devised to verify what are the effects of short-term LHRH and somatostatin ad- ministration during the fasting state of suckling and wean- ing rats. 2. Materials and methods 2.1. Animals * Correspondingauthor. Tel.: (55- 1l) 818-7303; Fax: (55-11 ) 8l 8-7402. Wistar rats aged 18 and 22 days, from the Histology and Embryology Department Animal Colony were used. 0167-0115/96/$15.00 Copyright © 1996 ElsevierScience B.V. All rights reserved. Pll S01 67-01 15(96)00013-4