Resistin, also known as Fizz3 or ADSF. is a protein found in murine adipose tissue and inflammatory lung exudates. The present studies found that resistin was released by explants of human adipose tissue but the release was quite variable ranging from 3 to 158 ng/g over 48 h. The release of resistin was 250% greater by explants of omental than by explants of human subcutaneous abdominal adipose tissue. Resistin release by adipocytes was negligible as compared to that by the non-fat cells of adipose tissue. Leptin formation by adipocytes was 8-fold greater than its formation by the non-fat cells, while the formation of PAI-1 by adipocytes was 38%, of that by the non-fat cells. The conversion of glucose to lactate as well as the formation of PGE(2) and IL-8 was approximately 15 /, of that by the non-fat cells. In contrast the release of IL-6 and IL-1beta by adipocytes was 4-7%, of that by the nonfat cells while the formation of resistin and IL-10 by adipocytes was 2%, of that by non-fat cells. The release of adiponectin by explants ranged from 1000 to 5000 ng/g over 48h but did not correlate with that of resistin. The present data suggest that resistin release by explants of human adipose tissue in primary culture is largely derived from the non-fat cells present in the explants. (C) 2002 Elsevier Science (USA). All rights reserved.