A Factor associated with ‘Visking’ Tubing capable of Antagonizing Insulin

DURING the investigation of the insulin antagonism associated with human serum albumin1, ‘Visking’ tubing (Visking Corporation, Chicago, U.S.A,) was used for ultrafiltration and dialysis of protein solutions. The tubing itself has since been found to give rise to a substance which antagonizes insulin and which appears in the following circumstances: (1) When distilled water is ultrafiltered through 7-ft. of heavy grade ‘Visking’ tubing (27/32 in. inflated diameter) supported by ‘Terylene’ net, under a negative pressure of 40–50 cm. mercury, over a period of three days. (2) When 7 ft. light grade ‘Visking’ tubing (18/32 in.) is filled with water and suspended in changes of distilled water for 2–7 days, that is, used as dialysis tubing.