Hormonal regulation of insulin-like growth factor binding proteins and insulin-like growth factor I (IGF-I) secretion in porcine stromal-vascular cultures.

We examined the time course of insulin-like growth factor binding protein (IGFBP) secretion and hormonal regulation of IGFBP and IGF-I secretion in porcine stromal vascular (S-V) cultures. Primary cultures of S-V cells derived from porcine adipose tissue were exposed to serum-free media with or without hormone treatment. Time course studies indicated that secretion of four IGFBP (IGFBP-1, -2, -3 and -4) by porcine S-V cells increased with time during the first 3 d after the switch to serum-free conditions and then decreased gradually. Growth hormone treatment stimulated secretion of each IGFBP by 47 +/- 4.7, 46 +/- 10.2, 70 +/- 13.2, and 49 +/- 5.6%, respectively, over control levels. The secretion of IGFBP-1, -2, -3, and -4 was enhanced by 91 +/- 18, 80 +/- 16, 74 +/- 12, and 263 +/- 48%, respectively, in T4-treated S-V cultures compared with untreated cultures. In contrast, dexamethasone reduced the abundance of the IGFBP by 28 to 50% of control levels. Insulin-like growth factor I secretion (844.63 +/- 35.98 pg/mL) in vitro (3 d conditioned media) was increased (P < .05) by GH (1,302.45 +/- 12.95 pg/mL) and T4 (1,291.60 +/- 86.4 pg/mL) and decreased (P < .05) by dexamethasone (552.5 +/- 30.2 pg/mL) (n = 4, S-V cell pools, P < .05). In addition to preadipocytes, other cells in S-V cultures also secrete IGFBP. In conclusion, the secretion of IGF-I and IGFBP by S-V cells is differentially regulated by hormones in vitro.