부산대학교 도서관

Abstract. Adult beagle bitches (20 to 101 months old) received medroxyprogesterone acetate (MPA; 75 mg/kg, im) or control vehicle at 3 month intervals. Changes in serum concentrations of GH, insulin and glucose were determined in 18 MPA-treated and 6 of 12 control bitches at 0, 2, 4, 8, 16 and 17–24 months of treatment (Exp. I). GH, LH and cortisol responsiveness to combined im injection of TRH (10 μg/kg), GnRH (10 μg/kg), and ACTH (5 μg/kg) was determined in 9 MPA-treated and 9 control bitches at 17 months of treatment (Exp. II). In Exp. I, serum concentrations of GH at month 2 (2.6 ± 0.3 μg/l), 4 (3.0 ± 0.3 μg/l), 8 (4.0 ± 1.2 μg/l), 16 (8.5 ± 1.7 μg/l), and 17–24 (21.2 ± 4.1 μg/l) of treatment were greater (P< 0.05) than pretreatment (1.4 ± 0.07 μg/l) and control (1.5 ± 0.1 μg/l) levels. The increase in GH at 2 months preceded (N = 4) or coincided (N = 2) with the development of hyperinsulinaemia and insulin resistance in 6 of the 18 treated bitches, two of which became diabetic by 17 months of MPA treatment. GH (24.6 ± 5.0 vs 11.4 ± 2.1 μg/l) and insulin (308 ± 77 vs 119 ± 9 pmol/l) concentrations were greater (P< 0.05) in older (49 ± 4 months; N = 12) than in the younger (26 ± 2 months; N = 6) treated bitches at 17–24 months of MPA treatment. In Exp. II, pretreatment concentrations of GH were increased (9.8 ± 3.0 vs 1.4 ± 0.1 μg/l, P< 0.01), cortisol levels decreased (12 ± 5 vs 72 ± 10 nmol/l, P< 0.01) and LH concentrations (0.9 ± 0.2 μg/l) unaffected in MPA-treated bitches. After injection of tropic hormones, GH was unchanged, whereas the rises in LH and cortisol levels were less (P< 0.01) in MPA-treated bitches than in control bitches. The results demonstrate that high doses of MPA increase GH concentrations within 2 months and that the GH overproduction and its diabetogenic-like effects were more pronounced in the older than in the younger treated bitches.