Occurrence of bombesin and alytesin in extracts of the skin of three European discoglossid frogs and pharmacological actions of bombesin on extravascular smooth muscle

1. Methanol extracts of the skin of Bombina bombina and Bombina variegata variegata, two European discoglossid frogs, contain an active tetradecapeptide, bombesin. Alytesin, a tetradecapeptide strictly related to bombesin is present in extracts of the skin of Alytes obstetricans, another European discoglossid frog. The American frog Rana pipiens, contains in its skin ranatensin, an endecapeptide related to bombesin and alytesin. 2. Passage of crude skin extracts of Bombina through a column of alumina yields eluates which may be considered free of other peptide contaminants and are suitable for the isolation of bombesin in a pure form. 3. Bombesin has a stimulant action on several preparations of intestinal, uterine and urinary tract smooth muscle. Sometimes the effect is easily repeatable and shows a fair proportionality to the dose, but at other times a prompt and intense tachyphylaxis is observed. Other smooth muscle preparations are poorly sensitive or insensitive to bombesin. The rat uterus, the kitten small intestine, the guinea-pig colon and the rat urinary bladder may be used for the quantitative bioassay of bombesin. 4. Bombesin-like peptides may easily be distinguished from all other naturally occurring peptides by parallel assay. They constitute a new group of active peptides possessing a peculiar spectrum of activity

The use of preparations of urinary bladder smooth muscle for bioassay of and discrimination between polypeptides.

Eleven polypeptides, two prostaglandins and three amines were assayed, in parallel, by measurement of their spasmogenic effect on the isolated urinary bladder of eight animal species, the in situ bladder of three species and the isolated ureter of three species. Several of the smooth muscle preparations examined proved to be sensitive and suitable test-objects for the quantitative bioassay of different peptides. At the same time they appeared to be useful for discriminating not only between peptides belonging to different groups, but also between members of the same peptide family. It is tentatively suggested that biogenic peptides may interfere in the physiological control of motility and tone of the urinary tract smooth muscle

Bioassay of vasopressin on the rabbit isolated urinary bladder.

The rabbit isolated urinary bladder contracted in the presence of Lys8-vasopressin from threshold concentrations of 5 to 30 μ ml−1 (0·02 to 0·11 ng ml−1). Responses were proportional to the dose used. The tissue gave satisfactory results either fresh or after storage for several days in cold Tyrode or Krebs solution (3–4°). The preparation also contracted in the presence of oxytocin, but it was 7 to 20 times less sensitive to this peptide. A number of other peptides and amines known to stimulate smooth muscle showed low activity on the rabbit urinary bladder and, occasionally, intense tachyphylaxis

The tachykinin peptide family

The tachykinin peptide family certainly represents one of the largest peptide families described in the animal organism. So far, more than 40 tachykinins have been isolated from invertebrate (insects, worms, and molluscs), protochordate, and vertebrate (skin, gastrointestinal tract, peripheral and central nervous system) tissues. Substance P (SP), first identified by bioassay as early as 1931 but sequenced only in 1971, several years after the elucidation of the structure of eledoisin from molluscan tissues and of physalaemin from amphibian skin, may be considered as a prototype of the tachykinins. Hitherto, as many as 19 tachykinins have been isolated from amphibian integument, and eight additional peptides have been isolated from amphibian gut and brain. Counterparts of skin tachykinins in mammalian tissues are SP, neurokinin A, and neurokinin B. Three main receptor subtypes for the tachykinins have been identified (NK1, NK2, and NK3), but their number is probably destined to increase. It is obvious that the peripheral and central effects of the tachykinins may substantially vary depending on the activation of different receptor subtypes. Matters are further complicated by the frequent capacity of the single tachykinins to bind, although with different affinity, to more receptors. It has been recognized that tachykinins have a variety of effects in physiological and pathological conditions, and there is evidence suggesting intrinsic neuroprotective and neurodegenerative properties of these neuropeptides. This review provides an update on the current body of knowledge regarding tachykinin occurrence and distribution in the animal kingdom, from the lowest invertebrates to man, and the physiological and pharmacological actions of tachykinins outlining the pregnant importance of this large peptide family

The action of polypeptides, amines and prostaglandins on isolated smooth muscle preparations of seminal vesicles and deferent ducts

The spasmogenic effect of 11 biogenic polypeptides, 2 prostaglandins and 3 amines was assayed, in parallel, on the isolated seminal vesicles and deferent ducts of the rat, guinea pig and hamster. The smooth muscle preparations were contracted by most of the examined compounds, but none of the preparations appeared to be particularly sensitive, and not infrequently bioassay was made difficult by tachyphylaxis. Thus, the smooth muscle preparations of the male genital tract, although containing receptors for biogenic polypeptides and amines, cannot be considered as test objects of first choice in the qualitative and quantitative bioassay of these compounds

Neuropeptide Y release by pumiliotoxin-B in electrically stimulated mouse vas deferens: an immunohistochemical study

(I.F.= 2,635