An isoelectric focusing study of seasonal variation in rattlesnake venom proteins.

Adult specimens of seven southern Pacific rattlesnakes (Crotalus viridis helleri), four northern black-tailed rattlesnakes (Crotalus molossus molossus), and six western diamondback rattlesnakes (Crotalus atrox) were housed under controlled light and temperature and milked of venom monthly for 20 months. Ambient conditions were modelled to simulate seasonal change. Weighed amounts of lyophilized venom from each snake were compared chronologically for variation in isoelectric focusing patterns, using natural and immobilized gradients. No variation in patterns was evident over this time period for any individual snake. However, intraspecific differences were obvious in the venom samples. The pattern seems indicative of a species, however, concentration of various protein constituents seems individual and genetically "fingerprinted'. Unlike other physiological functions that demonstrate cyclicity in response to temperature and photoperiod, concentration ratios of venom components appear to be constant regardless of external cues. These findings may further emphasize the medical importance of treating snakebite victims symptomatically as individuals. A variation exists in the components of venoms of any given species, as well as in the physiological sensitivities of humans to a venom.