SDS-PAGE analysis showed that 39.7% of the venoms analyzed were crotamine-positive, a result similar to Francischetti et al. (2000) and More et al. (2007), in disagreement with Schenberg (1959b), should be noted that the region of this study was not covered by the author. However, the venom extracted from newborns revealed

the presence of crotamine, diverging from Furtado et al. (2003) that also used newborn polled venom and did not find this protein in this age range. It is noteworthy to mention that the individual RP-HPLC analyses this website of the venoms employed throughout this work corroborated the presence or absence of crotamine in the venoms as assessed by SDS-PAGE. Moreover, since the UV-detection if the RP-HPLC profiles are more precise and sensitive than the gel staining, the phenomenon of the presence or absence of crotamine was confirmed, e.g., there is no concentration variation: either the venom is crotamine positive or it is negative. The RP-HPLC

chromatograms learn more also evidenced variations in intra- and inter-group protein concentrations (Fig. 1B). Variations in the presence or absence of proteins and their concentrations had already been established in studies on individual samples. Francischetti et al. (2000) showed differences between the eight samples and the reference venom when evaluating the chromatograms obtained from Cdt snakes originating from the Brazilian state of Minas Gerais. Studies of Crotalus durissus cumanensis snakes developed in Venezuela and Colombia also evidenced differences Phospholipase D1 in chromatographic profiles in relation

to the variations of determinate proteins as well as their concentrations. These differences were attributed to geographical variations in the snakes studied ( Aguilar et al., 2007; Céspedes et al., 2010). In the case of the Cdt venom, some questions remain: how is crotoxin assembled when there is more than one crotapotin and more than one PLA2 subunit? Is crotoxin static, or does it reassemble within the venom gland? Where does the variability occur (if so)? Are the resultant crotoxins pharmacologically and/or immunologically different? Studies on the venom of snakes from the families Elapidae and Viperidae evidenced, besides isoforms of known proteins ( Ponce-Soto et al., 2010), chromatographic differences and changes in protein concentrations. This phenomenon was attributed to the permanence of the animal in captivity ( Modahl et al., 2010). In this context, Toyama et al. (2003) observed two isoforms of crotamine in the Cdt venom, isolated after three chromatographic steps. They presented different actions in the muscular contractions in the phrenic nerve of the diaphragm in mice. In other subspecies of Crotalus, different isoforms of crotapotin and phospholipase A2 were also found, with variations in both their concentrations and enzymatic activities ( De Oliveira et al.