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The action of gastrin-releasing peptide and a GRP antagonist on avian acid secretion
38 OLIGONUCLEOTIDES AS PROBES FOR HYBRIDISATION : IDENTIFICATION OF TWO VIP mRNA'S JM Byrne, PM Jones and SR Bloom, Department of Endocrinology, Royal Postgraduate Medical School, Hammersmith Hospital, Ducane road, London W12 ONN, U.K. Study of gene structure and expression by hybridisation processes has provided many new insights in this area of investigation. Until recently this has generally involved the use of cDNA and/or cRNA probes. These probes have tended to range from a few hundred to several thousand base pairs and their synthesis can involve a number of steps. For example, using the polymerase chain reaction to synthesise probes produces DNA fragments which must sequenced and/or cloned into a suitable vector for amplification and reverse transcription purposes. Endlabelling oligonucleotides with terminal deoxynucleotidyl transferase bypasses the more tedious steps of cDNA probe manufacture. The oligonucleotides involved are relatively short (18-50bp) and can be labeled 'hot from the press' immediately after synthesis. By using large quantities of radioactive isotope in the labelling reaction, probes are produced with high specific activities, which are of similar sensitivity to random primer labelled, double stranded DNA probes. One of the applications of these probes is in the analysis of mRNA structure. For example, the VIP gene has been reported to give rise to a mature transcript of 1.7Kb. However, in the rat anterior pituitary 2 transcripts,one of 1.7Kb and one of 1.1Kb are detected. Use of oligonucleotides as specific hybridisation probes strongly suggests that this polymorphisim is the result of differential use of an alternate poly-adenalation signal in the 3' untranslated region 6of the VIP mRNA.
THE ACTION OF GASTRIN-RELEASING PEPTIDE AND A GRP ANTAGONIST ON AVIAN ACID SECRETION. B.J. CAMPBELL, A. GARNER, R. DIMALINE AND G.J. DOCKRAY. Dept. Physiology, University of Liverpool, Liverpool, U.K. Avian gastrin-releasing peptide (GRP) exists as a 27-residue peptide (GRP27) and its C-terminal hexapeptide GRP6, which occur in endocrine cells of the acid-secreting part of the stomach (the proventiculus). We have examined the actions of GRP27 and GRP6 on acid secretion in the anaesthetised turkey. The proventriculus lumen was perfused with saline (37"C, 5 ml/min.) and back-titrating to starting pH with 20mM NaOH. Rapid i.v. injections of natural chicken GRP27 increased acid secretion in the dose range 1.5 to 25 pmol/kg; the chemically related peptide bombesin 14 was approximately equipotent with GRP27, but GRP6 was virtually inactive at doses 1000 times higher. The synthetic C-terminal decapeptide of chicken gastrin (CG 10ns) also increased acid secretion in doses from t00 to 1600 pmol/kg. The GRP-antagonist (CHt02-CHCOHis-Trp-AIa-Val-D-Ala-His-Leu-NHCHs [ICI 216140], at a dose of 50pg/kg i.v., s~gnifieantly reduced the peak increment in acid secretion in response to 6 pmol/kg GRP27 from 75.67±10.23 to 4.65±5.09/~mol/10 rain (mean ± S.E., n=5; p<0.05,t-test). However, secretion stimulated by 400 pmol/kg CG 10ns ( 90.80_+4.97 ~mol./10min.) was not reduced by the antagonist ( 89.38±5.66, nffi5 ). COI~LI,ISIONS~ 1.) GRP27 and CGl0ns are potent stimulants of avian acid secretion; 2.) a GRP-antagonist specifically inhibits GRP-stimulated but not gastrin-stimulated acid secretion; 3.) it should now be possible to use this antagonist as a tool to examine the role of endogenous GRP in the control of acid secretion.
THE ACTION OF GASTRIN-RELEASING PEPTIDE AND A GRP ANTAGONIST ON AVIAN ACID SECRETION. B.J. CAMPBELL, A. GARNER, R. DIMALINE AND G.J. DOCKRAY. Dept. Physiology, University of Liverpool, Liverpool, U.K. Avian gastrin-releasing peptide (GRP) exists as a 27-residue peptide (GRP27) and its C-terminal hexapeptide GRP6, which occur in endocrine cells of the acid-secreting part of the stomach (the proventiculus). We have examined the actions of GRP27 and GRP6 on acid secretion in the anaesthetised turkey. The proventriculus lumen was perfused with saline (37"C, 5 ml/min.) and back-titrating to starting pH with 20mM NaOH. Rapid i.v. injections of natural chicken GRP27 increased acid secretion in the dose range 1.5 to 25 pmol/kg; the chemically related peptide bombesin 14 was approximately equipotent with GRP27, but GRP6 was virtually inactive at doses 1000 times higher. The synthetic C-terminal decapeptide of chicken gastrin (CG 10ns) also increased acid secretion in doses from t00 to 1600 pmol/kg. The GRP-antagonist (CHt02-CHCOHis-Trp-AIa-Val-D-Ala-His-Leu-NHCHs [ICI 216140], at a dose of 50pg/kg i.v., s~gnifieantly reduced the peak increment in acid secretion in response to 6 pmol/kg GRP27 from 75.67±10.23 to 4.65±5.09/~mol/10 rain (mean ± S.E., n=5; p<0.05,t-test). However, secretion stimulated by 400 pmol/kg CG 10ns ( 90.80_+4.97 ~mol./10min.) was not reduced by the antagonist ( 89.38±5.66, nffi5 ). COI~LI,ISIONS~ 1.) GRP27 and CGl0ns are potent stimulants of avian acid secretion; 2.) a GRP-antagonist specifically inhibits GRP-stimulated but not gastrin-stimulated acid secretion; 3.) it should now be possible to use this antagonist as a tool to examine the role of endogenous GRP in the control of acid secretion.