TRANSFORMING GROWTH-FACTOR-ALPHA AND ATRIAL-NATRIURETIC-PEPTIDE IN WHITE ADIPOSE-TISSUE DEPOTS IN RATS

To detect the presence in adipose tissue of peptides known to affect tissue growth and to investigate potential regional differences, epididymal and perirenal adipose tissue depots from male Sprague-Dawley rats were separated into adipocyte and stroma-vascular fractions by collagenase digestion, sequential centrifugation and filtration. Identity and integrity of the fractions were demonstrated by light and electron microscopy, while dose-response curves for angiotensin-converting enzyme (ACE) were performed, revealing maintained functional capacity of the stroma-vascular fraction. ACE, atrial natriuretic peptide (ANP), and transforming growth factor-alpha (TGF-alpha) concentrations were significantly greater in epididymal than perirenal stroma-vascular tissue. Adipocyte fractions from both depots contained significant concentrations of ANP and TGF-alpha. There was no detectable ACE in the adipocyte fractions, indicating that no contaminating stromal-vascular cells were present in these fractions. These data show significant concentrations of peptides with effects on growth in subfractions of adipose tissue and demonstrate regional differences in concentrations between fat depots.