Litorin

Effect of N-terminal tripeptides of bombesin, litorin, and their analogue on body temperature and vasomotor responses.[Pubmed:18399281]

Bull Exp Biol Med. 2007 Aug;144(2):207-9.

Intranasal administration of bombesin caused hypothermia in rats maintained under cold conditions. N-terminal tripeptide of bombesin exhibits intrinsic vasomotor activity, while intranasal administration of its modified analogue produced a more potent hypothermic effect than intranasal bombesin.

In vitro evaluation of (99m)Tc-EDDA/tricine-HYNIC-Q-Litorin in gastrin-releasing peptide receptor positive tumor cell lines.[Pubmed:23301856]

J Drug Target. 2013 May;21(4):383-8.

Bombesin and its derivatives exhibit a high affinity for gastrin-releasing peptide receptor (GRPr), which is over-expressed in a variety of human cancers (prostate, pancreatic, lung, etc.). The aim of this study was to investigate the in vitro potential of the hydrazinonicotinamide (HYNIC)-Q-Litorin. (99m)Tc labeling was performed by using different co-ligands: tricine and ethylenediamine diacetic acid (EDDA). The radiochemical stability of radiolabeled peptide conjugates was checked at room temperature and in cysteine solution up to 24 h. The in vitro cell uptake of (99m)Tc-EDDA-HYNIC-Q-Litorin and (99m)Tc-tricine-HYNIC-Q-Litorin were evaluated on pancreatic tumor and control cell lines. Optimum specific activity and incubation time were determined for all the cell lines. The results showed that the cell uptake of the radiolabeled peptide conjugates in tumor cell lines were higher than in the control cell line. The findings of this study indicated the need for further development of in vivo study as a radiopharmaceutical for pancreatic tumor imaging.

Radiolabeling of bombesin-like peptide with 99mTc: 99mTc-litorin and biodistribution in rats.[Pubmed:17760415]

Bioconjug Chem. 2007 Sep-Oct;18(5):1516-20.

Bombesin-like peptides are related to several human cancer receptors, including small cell lung, prostate, breast, colon, and pancreatic cancers. Litorin, an amphibian bombesin peptide derivative, is found to stimulate the contraction of smooth muscle, to stimulate gastrin, gastric acid, and pancreatic secretion, and to suppress the nutriment in in vivo experiments. In the present study, Litorin was labeled with 99mTc by the stannous chloride procedure. Labeling yield is 95 +/- 1.4%, as determined by radio thin layer chromatography (RTLC) and radio high performance chromatography (RHPLC). Results of in vitro studies demonstrated a high stability in serum and cysteine solutions. In vivo biodistribution was investigated with normal male Albino Wistar rats. Biodistribution data showed fast clearance, low intestinal accumulation, and significant uptake in bombesin/gastrin releasing peptide (BN/GRP) receptor rich tissues such as the pancreas (23.56 +/- 0.01 %ID/g 30 min pi). It can be blocked partially by previous administration of 'cold' Litorin. The results showed specificity of the uptake. As 99mTc-Litorin displays good radiolabeling and biodistribution, it is a potentially useful radiopharmaceutical for detection of bombesin receptor-expressing cancers.

Central litorin injection is associated with primary anorexigenic effects that coincide with activation of the magnocellular division of the paraventricular nucleus.[Pubmed:20116849]

Neuropeptides. 2010 Jun;44(3):247-52.

The central mechanism that mediates Litorin-induced satiety is poorly understood, and has not been studied in a non-mammalian species. Therefore, the aim of this study was to determine if Litorin-induced satiety in an alternative vertebrate model, the chick, and to elucidate some of the central mechanisms that are associated with this response. In Experiment 1, chicks responded to intracerebroventricular (ICV) injection of Litorin with reduced food intake at all doses tested (0.1, 1.0, and 10 nmol), while concurrently, an anti-dipsogenic effect was observed in the two higher doses tested. Whole blood glucose concentrations were not affected. In Experiment 2, chicks that were food-withheld did not reduce their water intake after ICV Litorin injection. To determine if Litorin affected behaviors unrelated to ingestion, a comprehensive behavior analysis was conducted as Experiment 3. Of the behaviors observed, only the number of feeding pecks was reduced. Other behaviors such as movement, defecation, escape, posture, or deep rest were not affected. Lastly, in Experiment 4, Litorin-treated chicks had an increased number of c-Fos immunoreactive cells in the magnocellular division of the paraventricular nucleus. The arcuate nucleus, dorsomedial nucleus, lateral hypothalamus, parvicellular division of the paraventricular nucleus, suprachiasmatic nucleus, periventricular nucleus and the ventromedial hypothalamus were not affected. Therefore, we conclude that ICV Litorin causes anorexigenic effects in chicks associated with changes in hypothalamic chemistry that appear to be behavior specific.

Comparison of the peptide structural requirements for high affinity interaction with bombesin receptors.[Pubmed:8788416]

Eur J Pharmacol. 1995 Dec 27;294(1):55-69.

Recently it has been established that both a gastrin-releasing peptide (GRP)-preferring bombesin receptor and a neuromedin B-preferring bombesin receptor mediate the mammalian actions of bombesin-related peptides. Because many tissues used for studies of the structure-activity relationship of these peptides possess both receptor subtypes and none possess only the neuromedin B-preferring subtype, there is minimal information on the peptide structural features determining receptor selectivity and it is unknown whether the determinants of agonism at both bombesin receptor subtypes are similar. In the present study we have used native cells either possessing only one bombesin receptor subtype or stably transfected with one subtype to study in detail the peptide structural requirements for interacting and activating each receptor subtype. For the naturally occurring agonists, at the GRP-preferring bombesin receptor the relative affinities were Litorin = ranatensin = bombesin > GRP >> neuromedin B, phylloLitorin and at the neuromedin B-preferring bombesin receptor were Litorin = neuromedin B = ranatensin > bombesin, phylloLitorin >> GRP. For the GRP-preferring bombesin receptor the heptapeptide and for the neuromedin B-preferring bombesin receptor the octapeptide was the minimal carboxyl fragment interacting with the receptor/or causing biologic activity, and the nonapeptide and full decapeptide, respectively, were the minimal required for full affinity. Making neuromedin B more bombesin- or GRP-like by replacing amino acids in position 3, 6, and 9 demonstrated that position 3 was the most important, followed by position 9 for receptor subtype selectivity. A conformationally restricted GRP analogue, [D-Cys6,D-Ala11,Cys14]bombesin-(6-14) had a significantly higher affinity for GRP-preferring bombesin receptor than NMB receptor. These results demonstrate that: (1) the structure-function relations for the two mammalian bombesin receptors have important differences; (2) suggest that the active conformation of neuromedin B must differ markedly from the beta-sheet model proposed for GRP; and (3) suggest that one important function of the NH2 terminus of GRP and neuromedin B is determining receptor subtype selectivity.

Litorin suppresses food intake in rats.[Pubmed:6290821]

Life Sci. 1982 Aug 16;31(7):685-92.

Litorin (LIT), a bombesin-like nonapeptide, decreased food intake in rats in a dose-related manner after parenteral injection. LIT decreased deprivation-induced water intake only at a dose much higher than required to suppress feeding. LIT administration did not significantly alter the frequency of observed feeding-associated behaviors, nor did it result in subsequent aversion to an associated novel solution. Litorin shares with bombesin structural features and pharmacological actions that include the suppression of food intake in a manner that mimics natural satiation.

Parallel bioassay of bombesin and litorin, a bombesin-like peptide from the skin of Litoria aurea.[Pubmed:1201379]

Br J Pharmacol. 1975 Oct;55(2):213-9.

The spectrum of biological activity exhibited by Litorin, a bombesin-like nonapeptide found in extracts of the skin of the Australian leptodactylid frog Litoria aurea was compared with that exhibited by the tetradecapeptide bombesin. 2 Litorin proved to be more potent than bombesin on isolated smooth muscle preparations and on the urinary bladder in situ. However, it was less potent on dog systemic blood pressure and kidney vasculature activation of the renen-angiotensin system being slight or lacking. 3 Gastrin release and acid secretion produced by Litorin was more rapid in onset but less intense and less sustained than that elicited by bombesin. The same could be observed for pancreatic secretion. 4 Gall bladder contraction stimulated by Litorin was probably caused by a double action of the peptide, directly on the bladder smooth muscle, and indirectly by cholecystokinin release. 5 In its effects on the myo-electric activity of the dog duodenum (inhibition of spikes and increase in frequency of pacesetter potentials leading to the appearance of a sequence of slow and small potentials) Litorin possessed approximately 50 to 70% of the activity of bombesin.