Two distinct insulin-related molecules in the guinea pig: immunological and biochemical characterization of insulin-like immunoactivity from extrapancreatic tissues of the guinea pig.

In this study we extracted guinea pig brain and testis with; the extract was adsorbed to and eluted from cartridges (the Sep-Pak C18 procedure). We found this procedure superior for recovering crystalline insulin added to buffers or tissues, and for recovering endogenous insulin from plasma, but inferior for recovery of insulin from tissues. However, we did find 'rat/pork' type-insulin in guinea pig brain and testis (5-50 pg/g wet weight tissue). Our results with the Sep-Pak C18 procedures were reproduced by four other laboratories (who found 4-60 pg/g wet weight of tissue) and similar findings were also obtained by an independent investigator. Thus, we conclude that extrapancreatic tissues of guinea pigs have a second type of insulin-related material that is more typical of other mammalian insulins, but that the amount recovered is dependent upon the extraction procedure utilized.