Failure of Guinea Pig Antibodies to Beef Insulin, Chicken Insulin, and Cod Insulin to Neutralize Capybara Insulin

Abstract

Guinea pig and coypu insulins are the only mammalian insulins known to be non-neutralizable by antibody to beef insulin. A third non-neutralizable mammalian insulin, that of the capybara (carpincho, or hydrochoerus hydrochoerus) has been identified. Capybara pancreas yielded 0.5 U. extractable insulin per gram. An amount of guinea pig antibody to beef insulin sufficient to neutralize thirty times as much beef insulin did not significantly alter the increase in glycogen content produced by pancreatic capybara insulin in the mouse hemidiaphragm in vitro. Both 50 mU. capybara insulin and 50 mil capybara insulin plus 150 mU. antibody to beef insulin when injected into mice produced about the same number of convulsions and lowered the blood glucose to about the same mean level as did 50 raU. beef insulin alone. Mice injected with 50 mU. beef insulin plus 150 mU. antibody to beef insulin did not convulse and had a mean blood glucose of 156 mg. per 100 ml. Antibody to chicken insulin and antibody to cod insulin did not significantly alter the increase in glycogen content produced by pancreatic capybara insulin in the mouse hemidiaphragm in vitro. Capybara pancreatic extract cross-reacted with guinea pig antiserum to beef insulin in the passive cutaneous ana-phylaxis test.