Effect of the synthetic glucocorticoid, deflazacort, on body growth, pulsatile secretion of GH and thymolysis in the rat

Design: Deflazacort (DFZ) is a relatively new,glucocorticoid that has been reported to exhibit fewer side-effects than other commonly used corticoster oids. The present study was designed to test the effects of DFZ on thymus g land involution (thymolysis), as compared with body growth and the secretor y pattern of GH in the rat. Beginning at 38 days of age, male animals were treated for 8 consecutive days by s.c. injection of DFZ (0.15 mg/day), cort isone (CORT) (5 mg/day) or vehicle (control, CTRL). Results: Both glucocorticoids had a similar thymolytic effect and caused gr owth failure. but the growth rate for the DFZ group was significantly highe r than that of the CORT group. On day 46, pulsatile GH secretion was quanti tated by blood sampling via an indwelling catheter at 10 min intervals for 6 h. GK was assayed by RIA and analyzed by multiparameter deconvolution. CO RT caused an increase in pulse frequency (5.8 +/- 0.4 (S.E.M.)) in comparis on to DFZ (4.4 +/- 0.4) and CTRL (3.8 +/- 0.3). Both glucocorticoids signif icantly shortened the interval between secretory bursts. In CTRL, animals t he interval between bursts was 69.3 +/- 4.5 min. In DFZ animals this was re duced to 58.5 +/- 7.1 min, and in CORT rats it was further reduced to 47.0 +/- 2.6 min. The mass of GH secreted per burst was reduced in CORT animals (52% of CTRL), while DFZ did not alter this parameter. A similar trend was observed for total GH production, with CORT causing a reduction and DFZ not affecting the secretion. Conclusion: Rats treated with glucocorticoid show a profound thymolytic eff ect, as well as important changes in growth. While CORT suppresses GH secre tion and alters its pulsatile mode of release, DFZ causes a less significan t alteration in the pattern of GH secretion and does not negatively affect the overall amount of GH secreted.