Transport of peptide hormones across isolated rat mesentery: effect of human serum-bound insulin.
The exchange of 125I-insulin, 125I-glucagon, 125I-proinsulin, 125I-growth hormone, 131I-albumin, 14C-inulin, and 14C-dextran across isolated rat mesentery was studied in a diffusion cell. The passage of immunoprecipitable porcine 125I-insulin (0.88 ng./ml.) was not affected by porcine proinsulin (145 ng./ml.), crystalline porcine insulin (17.4 ng./ml.), human growth hormone (87 ng./ml.), bovine serum albumin (4.5 mg./ml.), or normal guinea pig serum (840 mug. protein/ml.). However, the rate of insulin exchange was reduced by guinea pig anti-insulin antiserum and partially purified human serum-bound insulin (175 mug. protein/ml.). Bound insulin at the same concentration did not affect the exchange of 125I-glucagon, 125I-growth hormone, 14C-inulin, or 14C-dextran. Further purification of bound insulin by Sephadex G-100 chromatography yielded an approximately 45,000-molecular-weight fraction that at 5 mug. protein permilliliter allowed essentially no insulin transport. This same fraction of bound insulin significantly inhibited the disappearance of immunoprecipitable porcine 125I-insulin from the incubation medium of isolated rat hemidiaphragms. Theses studies suggest that the transport of insulin across biologic membranes, mesothelium, and possible endothelium is specifically inhibited by bound insulin, a circulating macromolecule that possesses insulin-like activity.
D000818:Animals; D001692:Biological Transport; D001798:Blood Proteins / Q000378:metabolism; D002417:Cattle; D003911:Dextrans / Q000378:metabolism; D004727:Endothelium / Q000502:physiology; D005934:Glucagon / Q000378:metabolism; D013006:Growth Hormone / Q000378:metabolism; D006728:Hormones / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D007330:Insulin Antibodies; D007444:Inulin / Q000378:metabolism; D046911:Macromolecular Substances; D008643:Mesentery / Q000502:physiology*; D011384:Proinsulin / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D012711:Serum Albumin, Radio-Iodinated / Q000378:metabolism; D013552:Swine
D001798:Blood Proteins; D003911:Dextrans; D006728:Hormones; D007328:Insulin; D007330:Insulin Antibodies; D046911:Macromolecular Substances; D012711:Serum Albumin, Radio-Iodinated; D013006:Growth Hormone; D007444:Inulin; D005934:Glucagon; D011384:Proinsulin