Binding characteristics of swine erythrocyte insulin receptors

Crossbred gilts (controls; n = 7) had 8.8 ± 1.1% (mean ± SEM) maximum binding of [ 125I]insulin to insulin receptors on erythrocytes. The number of insulin-binding sites per cell was 137 ± 19, with a binding affinity ranging from 7.4 x 107M⁻¹ to 11.2 x 107M⁻¹ and mean of 8.8 x 107M⁻¹. Pregnant sows (n = 5) had a significant increase (P < 0.01) in maximum binding due to an increase in number of receptor sites per cell. Lactating sows fed a high-fiber diet (n = 3) and a low-fiber diet (n = 4) did not develop a significant difference in maximum binding of insulin. Sows fed the low-fiber diet had a significantly higher number of binding sites and a significantly lower binding affinity than did sows fed a high-fiber diet. Receptor-binding affinity was lower in the low-fiber diet group than in cycling gilts, whereas data from sows fed the high-fiber diet did not differ from data for cycling gilts. Data from this study indicated that insulin receptors of swine erythrocytes have binding characteristics similar to those in other species. Pregnancy and diet will alter insulin receptor binding in swine.