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Isolation and chemical characterization of new peptides of the VIP family
S12 ISOLATION AND CHEMICAL CHARACTERIZATION OF NEW PEPTIDES OF THE VIP FAMILY Viktor Mutt, Department of Biochemistry II, Karolinska Institute, Box 60 400, S-I04 01 Stockholm, Sweden. The isolation of the, porcine, vasoactive intestinal polypeptide (VIP), some ten years ago, and the determination of its amino acid sequence was followed by the organic chemical synthesis of it and by the use of either natural VIP or of its synthetic replicate for the screening of the physiological, or pharmacological, activities of VIP, and for the raising of antisera by which the organ distribution of VIP, or at any rate VIP-like immunoreactivity, could be determined. Several unexpected activities were discovered, a few of which seem to suggest investigations on the possible use of exogenous VIP in clinical medicine. On the biochemical side it was shown that VIP is identical in the human, the porcine, the bovine, and the murine species. In this, mammalian VIP resembles glucagon. Such a degree of interspecies conservation does not apply to the, structurally, VIP-related secretin. Porcine secretin is indeed identical to bovine, but differs, albeit slightly, from the human form. VIP has been shown to be biosynthesized in a precursor protein together with a sfiructurally related hormonal polypeptide, PHI. In contrast to VIP the human, porcine and bovine PHI~ are nonidentical. C-terminally extended biosynthetic intermediate forms of secretin have been isolated from porcine intestinal tissue extracts and shown to exhibit secretin-like activities. The situation concerning VIP in this respect is not yet known. Of considerable interest is to determine the nature of the various less basic forms of VIP first demonstrated to be present in tissue extracts, by R. Dimaline and G.J. Dockray (Gastroenterology 75, 387-392, 1978). In collaboration with these workers we have, from extracts ofporcine intestine, isolated two such forms of immunoreactive VIP, and obtained evidence for the presence in such extracts of yet other forms. Work is in progress to determine whether some or all of them are artefacts formed during the isolation procedure, or naturally occurring polypeptides, possibly with at least some differences, qualitative or quantitative, in bioactivifiy to ordinary VIP.
EFFECTS OF VIP ON PROLACTINAND GROWTHHORMONESECRETIONBY GH CELLS. REGULATIONBY PERIPHERALHORMONE Danielle Gourdji,(*) Dominique Bataille , Nicole Buisson and Andr~e Tixier-Vidal. Laboratoire de neuroendocrinologie Cellulaire, Coll~ge de France 75231 Paris Cedex 05,(*) Centre CNRS-INSERM pharmacolo-Endocrinologie, BP 55055, 34033 Nontpellier Cedex, France.
The hypothesis for VIP being a Prolactin (PRL) releasing factor, acting on p i t u i t a r y via cAMP-dependent mechanisms, is now supported by a number of studies. The part ~ VIP in the multihormonal regulation of PRL secreting cells is nevertheless not clear so far, namely as compared to TRH. Indeed, long-term effects of VIP on PRL and GH secretion are almost ignored and the influence of peripheral hormones, such as estradiol 17~ (E2) or triiodotyronine (T3) on VIP-induced responses are unknown. This was investigated here using monolayers of GH clonal rat p i t u i t a r y cells, secreting b o t h PRL and GH, and precultured in serum supplemented (SS) or in serum free (SF) media. VIP or VIP related peptides-induced alteration of cAMP, PRL and GH were measured and compared to that induced by TRH in similar conditions. Ue show that : l ) VIP e l i c i t e d similar acute and transient rise in cAMP production in both SF and SS media, 2) VIP was able to stimulate PRL release in SF containing neither E2 nor T3 as well as in SS media, 3) By contrast with t h e i r respective positive and negative interaction with TRH, E2(O.5nM) decreased or abolished this stimulation while T3(50 pM) did not alter it. 4) A long-term exposure induced an increase in PRL production in both SS and SF media, 5) VIP also stimulated long-term production of GH, in SF medium only, 6) E2 and T3 respectively antagonized and respected VIP-induced long-term effects. Altogether these results indicate that not only VIP and TRH act on p i t u i t a r y cells via different i n t r a c e l l u l a r mechanisms, buth also that their effects are differen-n-t-ly dependent on the hormonal environment.
EFFECTS OF VIP ON PROLACTINAND GROWTHHORMONESECRETIONBY GH CELLS. REGULATIONBY PERIPHERALHORMONE Danielle Gourdji,(*) Dominique Bataille , Nicole Buisson and Andr~e Tixier-Vidal. Laboratoire de neuroendocrinologie Cellulaire, Coll~ge de France 75231 Paris Cedex 05,(*) Centre CNRS-INSERM pharmacolo-Endocrinologie, BP 55055, 34033 Nontpellier Cedex, France.
The hypothesis for VIP being a Prolactin (PRL) releasing factor, acting on p i t u i t a r y via cAMP-dependent mechanisms, is now supported by a number of studies. The part ~ VIP in the multihormonal regulation of PRL secreting cells is nevertheless not clear so far, namely as compared to TRH. Indeed, long-term effects of VIP on PRL and GH secretion are almost ignored and the influence of peripheral hormones, such as estradiol 17~ (E2) or triiodotyronine (T3) on VIP-induced responses are unknown. This was investigated here using monolayers of GH clonal rat p i t u i t a r y cells, secreting b o t h PRL and GH, and precultured in serum supplemented (SS) or in serum free (SF) media. VIP or VIP related peptides-induced alteration of cAMP, PRL and GH were measured and compared to that induced by TRH in similar conditions. Ue show that : l ) VIP e l i c i t e d similar acute and transient rise in cAMP production in both SF and SS media, 2) VIP was able to stimulate PRL release in SF containing neither E2 nor T3 as well as in SS media, 3) By contrast with t h e i r respective positive and negative interaction with TRH, E2(O.5nM) decreased or abolished this stimulation while T3(50 pM) did not alter it. 4) A long-term exposure induced an increase in PRL production in both SS and SF media, 5) VIP also stimulated long-term production of GH, in SF medium only, 6) E2 and T3 respectively antagonized and respected VIP-induced long-term effects. Altogether these results indicate that not only VIP and TRH act on p i t u i t a r y cells via different i n t r a c e l l u l a r mechanisms, buth also that their effects are differen-n-t-ly dependent on the hormonal environment.