Lactogenic and Somatotropic Binding Sites in Liver Membranes of Rats with Renal Insufficiency

Binding sites for human GH (hGH) were studied in liver membranes of rats with chronic renal insufficiency (CRI) associated with marked growth retardation. A subtotal nephrectomy was performed in young female rats. One month after the nephrectomy, the animals with a plasma creatinine level 3 times or more that of controls were studied; their mean statural gain was 56% that of controls. The specific binding of [125I]hGH to microsomal membranes of rats with CRI was low (40% that of controls). The number of binding sites rather than the affinity of the binding was affected; both the lactogenic and somatotropic sites were decreased, as judged from the binding of ovine [125I]PRL and bovine [125I]GH. The binding sites of the plasma membranes as well as those of the Golgi fractions, were reduced. In plasma membranes of rats with CRI, the specific binding of glucagon was low, and the specific binding of insulin was elevated; these modifications were associated with a high plasma glucagon level and a decreased insulinemia in rats with CRI, but no modification of plasma GH and PRL levels was found. Thus, the hormone level does not appear to regulate the GH-binding sites in this system. The link between the growth defect and the decreased number of GH-binding sites in the liver membranes of rats with CRI remains to be established.