1. In vitro and in vivo biological activities of PG-KII, a novel kassinin-like peptide from the skin of the Australian frog, Pseudophryne güntheri
G Improta, M Broccardo, C Severini, V Erspamer Peptides. 1996;17(6):1003-8. doi: 10.1016/0196-9781(96)00140-4.
We compared the in vitro and in vivo biological activities of PG-KII (pGlu-Pro-Asn-Pro-Asp-Glu-Phe-Val-Gly-Leu-Met-NH2), a new peptide belonging to the tachykinin family, related to kassinin, isolated and sequenced from extracts of the skin of the Australian myobatrachid frog Pseudophryne güntheri, with those of the well-known tachykinins [substance P (SP), neurokinin A (NKA), neurokinin B (NKB), and kassinin (KASS)] to study its pharmacological and receptor profile. PG-KII always proved inactive in the in vitro and in vivo (gastric emptying) NK2 bioassays. It resulted equipotent to SP and more potent than KASS, NKA, and NKB in all in vitro smooth muscle preparations preferentially activated by the NK1-selective agonists. On an in vivo NK3 receptor-mediated function, gastric acid secretion, PG KII had a potency similar to that of NKB. In contracting guinea pig ileum, which contains NK1, NK2, NK3, and also new tachykinin receptor subtypes, PG-KII was more potent than SP, NKB, and NKA. The cholinergic antagonist, atropine, significantly reduced the guinea pig contractile activity of both PG-KII and NKB but not that of SP or NKA. Pretreatment with the NK1 selective antagonist, CP 96,345, and with the NK2-selective antagonist, MEN 10,376, modified neither the in vivo nor the in vitro effects of PG-KII. These findings indicate that PG-KII is neither an NK1 nor an NK2 receptor agonist but has a spectrum of biological actions close to that of the NK3 receptor agonists. PG-KII elicits strong contractile activity in guinea pig ileum. Administered centrally in the rat it regulates inhibition of gastric acid secretion.
2. Parallel bioassay of physalaemin and kassinin, a tachykinin dodecapeptide from the skin of the African frog Kassina senegalensis
G F Erspamer, V Erspamer, D Piccinelli Naunyn Schmiedebergs Arch Pharmacol. 1980 Feb;311(1):61-5. doi: 10.1007/BF00500303.
1. Kassinin, a tachykinin dodecapeptide isolated from the skin of the African frog Kassina senegalensis was submitted to parallel bioassay with physalaemin, eledoisin and substance P, three major representatives of the tachykinin peptide family. Bioassay was carried out on blood pressure, salivary secretion and isolated or in situ smooth muscle preparations. 2. As expected, kassinin possessed the entire spectrum of biological activity peculiar to the tachykinins. However, among the examined tachykinins kassinin was the poorest stimulant of salivary secretion and the weakest hypotensive agent, while displaying very powerful stimulant effects on different smooth muscle preparations, especially on isolated preparations of urinary bladder. 3. Kassinin differed from the other tachykinins also for its more gradual and sustained action on several in situ and isolated preparations. The peptide most similar to kassinin in its spectrum of activity was eledoisin. 4. Emphasis is laid on the possibility to dissociate the effects of the tachykinins on different target systems through changes in the N-moiety of the tachykinin molecule.
3. Parallel bioassay of bombesin and litorin, a bombesin-like peptide from the skin of Litoria aurea
R Endean, V Erspamer, G Falconieri Erspamer, G Improta, P Melchiorri, L Negri, N Sopranzi Br J Pharmacol. 1975 Oct;55(2):213-9. doi: 10.1111/j.1476-5381.1975.tb07630.x.
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.
