Les hormones neurohypophysaires des reptiles: Isolement de la mésotocine et de la vasotocine de la vipère Vipera aspis

Neuropeptide families: evolutionary perspectives

Examination of neuropeptide families can provide information about phyletic relationships and evolutionary processes. In this article the oxytocin/vasopressin family, growth hormone releasing factor (GRF) superfamily and the substance P/tachykinin family have been considered in detail because they have been isolated from an extraordinarily diverse array of species from several vertebrate classes and invertebrate phyla. More important is that the nucleotide sequence of mRNA or cDNA encoding many of these peptides has been determined, which has allowed evolutionary distances to be estimated based on the DNA mutation rate. The origin of a given family lies in a primordial gene that arose many millions of years ago, and through time, exon duplication and insertion, gene duplication, point mutation and exon loss, the family developed into the forms that are now recognised. For example, in birds, GRF and pituitary adenylate cyclase activating peptide (PACAP) are encoded by the same gene, which probably arose as a result of exon duplication and tandem insertion of the ancestral GRF gene. In mammals GRF is the sole product on one gene, and PACAP is the product of a gene that also produces PACAP-related peptide (PRP), which is homologous to GRF. Thus it appears that between birds and mammals the GRF/PACAP gene duplicated: exon loss gave rise to the mammalian GRF gene, while mutation led to the formation of the mammalian PRP/PACAP gene. The neuropeptide Y superfamily is considered briefly, as is cionin, which is an invertebrate peptide that is closely related to the mammalian gastrin/cholecystokinin family.

Circulating vasotocin in the snake Bothrops jararaca

1. There is biochemical and pharmacological evidence to suggest the presence of vasotocin in the blood and plasma of the snake Bothrops jararaca (Bj). 2. XE-64 extracts from Bj blood showed antidiuretic and hypotensive activities in rats and a contractile effect on rat isolated uterus, which was totally dialysable and inhibited by thioglycollate. 3. Extracts from Bj whole plasma presented an antidiuretic activity which was only partially dialysable. 4. The plasma extracts also showed oxytocic properties. 5. When EDTA and Sep-Pak C18 extraction were used, a better recovery and characterization of vasotocin by HPLC was obtained. 6. These results indicate the occurrence of free and bound circulating vasotocin in Bj, in an equilibrium dependent of its enzymatic hydrolysis.

Evolutionary specificity of hydrins, new hydroosmotic neuropeptides: occurrence of hydrin 2 (vasotocinyl-Gly) in the toad Bufo marinus but not in the viper Vipera aspis

Hydrin 2 (vasotocinyl-Gly), a hydroosmotic peptide resulting from differential processing of provasotocin and recently identified in frog neurohypophysis, has been looked for in the pituitary gland of an exotic toad (Bufo marinus) and of a reptile (Vipera aspis). Hydrin 2 has been found in the amphibian but not in the reptile. This result confirms the evolutionary specificity of hydrin 2 that has been identified only in frogs and toads but not in birds and reptiles. Occurrence of hydrin 2 is explained by its regulatory function on the water permeability of the skin of anurans.