Effect of anti-insulin receptor antibodies on insulin-sensitive phosphodiesterase in rat fat cells

Effect of sera with anti-insulin receptor antibodies (AIRS) on insulin-sensitive phosphodiesterase in rat fat cells was examined. AIRS activated the enzyme when incubated with intact fat cells. AIRS (1:400 dilution) were less potent for activation of the phosphodiesterase than insulin (3 nM), but were more potent for inhibition of 125I-insulin binding to fat cells than insulin. When insulin receptor of fat cells was destroyed with trypsin-treatment, AIRS as well as insulin completely lost the ability to activate the phosphodiesterase. These findings suggest that AIRS bind to or very near the insulin receptor and exhibit insulin-like biological effect of the phosphodiesterase activation.