MEASUREMENT OF SMALL QUANTITIES OF INSULIN-LIKE ACTIVITY WITH RAT ADIPOSE TISSUE. III. PERSISTENCE OF SERUM INSULIN-LIKE ACTIVITY AFTER PANCREATECTOMY*

Abstract

(1) Serum insulin-like activity (ILA), as measured on glucose oxidation by adipose tissue in vitro, persisted in significant amounts for up to 8 days after total pancreatectomy in dogs. This contrasts with the known disappearance of insulin activity, as measured on the rat hemidiaphragm, in postpancreatectomy serum. (2) In 5 dogs, serum ILA was measured daily after pancreatectomy. A significant decrease to about one-half the preoper-ative level occurred within 20 hours without further decline until death. (3) ILA of postpancreatectomy dog serum resembled insulin in that it was nondialyzable; stimulated the oxidation of glucose and also the incorporation of glucose carbon into glycogen and fatty acid of adipose tissue; was abolished by exposure to reduced glutathione; and could in part be extracted with acid ethanol. Although anti-insulin serum (AIS) failed to support the ILA of unmodified postpancreatectomy serum, AIS significantly suppressed the ILA of an acid ethanol extraction. (4) The persistence in serum from pancreac-tomized animals of detectable amounts of a form of insulin with long intravascular half life and without biologic activity in vivo is suggested.