Biochemical and Cytochemical Studies of Preadipocyte Differentiation in Serum-Free Culture of Porcine Stromal-Vascular Cells: Interaction of Dexamethasone and Growth Hormone

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Abstract
Stromal-vascular cells from adipose tissue of pigs 5–7 days of age were grown in serum for 2–3 days and switched to serum-free (insulin, transferrin and selenium) conditions ± test hormones for 6-7 days. The interaction of dexamethasone (DEX) and human growth hormone (hGH) was evaluated since glucocorticoids augment and hGH antagonizes the effect of insulin. Low lewels (1–10 nM) of DEX with insulin doubled (p < 0.05) specific activity of glycerol phosphate dehydrogenase (GPDH) and doubled (p < 0.05) the number of detectable fat cells relative to insulin alone. DEX with insulin enhanced the morphological differentiation of preadipocytes and markedly increased fat cell cluster numbers in the presence of hGH. Furthermore, 1–10 nM of DEX partially blocked (p > 0.05) the inhibitory effect of 10 nM hGH on GPDH activity, but 1–100 nM DEX had no effect (p > 0.05) on the ability of hGH to compromise lipid deposition. DEX alone (no insulin or hGH) induced the appearance of esterase-reactive but lipid-free cells. Cells with these characteristics were increased in number by DEX in the presence of hGH but were nearly absent in the presence of insulin and DEX. Therefore, transient exposure to GH in vivo may have no permanent effect on adipose tissue development in the continued presence of glucocorticoids.