Barb C R, Cox N M, Carlton C A, Chang W J, Randle R F
Animal Physiology Research Unit, USDA, ARS, Russell Research Center, Athens, Georgia 30613.
Proc Soc Exp Biol Med. 1992 Nov;201(2):223-8. doi: 10.3181/00379727-201-43503.
Diabetes mellitus was induced using streptozotocin in five gilts between 8 and 12 weeks of age. Gilts were maintained with exogenous insulin (INS) except during experimental periods. Four litter-mate gilts served as controls. At 9 months of age, all gilts were ovariectomized, and 30 days after ovariectomy, Experiment (Exp) 1 was conducted. Jugular vein catheters were inserted and blood samples were collected every 10 min for 8 hr. Experiment 2 was conducted when gilts were 11 months of age. Venous blood and cerebrospinal fluid (CSF) samples were collected in the absence (Phase I) or presence (Phase II) of INS therapy. In Experiment 1, plasma glucose concentrations were greater (P < 0.05) in diabetic (465 +/- 17 mg/100 ml) than in control (82 mg +/- 17 mg/100 ml) gilts, whereas serum INS was lower (P < 0.0001) in diabetic gilts (0.3 +/- 0.02 vs 0.9 +/- 0.05 ng/ml) and insulin-like growth factor-I was similar in diabetic and control gilts (32 +/- 3 vs 43 +/- 4 ng/ml, respectively). Mean serum GH concentration was 2-fold greater (P < 0.02) in diabetics (2.8 +/- 0.4 ng/ml) than in control gilts (1.2 +/- 0.2 ng/ml). Diabetic gilts exhibited a greater (P < 0.05) number of GH pulses than control gilts (3.2 +/- 0.4 vs 1.5 +/- 0.3/8 hr, respectively). In addition, GH pulse magnitude was markedly elevated (P < 0.02) in diabetic (5.8 +/- 0.4 ng/ml) compared with control gilts (3.3 +/- 0.6 ng/ml). Mean basal serum GH concentrations were greater (P < 0.07) in diabetic (2.2 +/- 0.5 ng/ml) compared with control gilts (1.0 +/- .1 ng/ml). In Experiment 2, CSF concentrations of insulin-like growth factor-I, INS, GH, and protein were similar for diabetic and control gilts in both phases. Serum GH levels were similar for diabetics and controls in Phase I, but were greater (P < 0.05) in diabetics than in controls in Phase II. CSF glucose levels were greater in diabetic than in control gilts in both the presence (P < 0.003) and absence (P < 0.0002) of INS therapy, whereas plasma glucose was greater (P < 0.003) in diabetic than in control gilts in the absence of INS, but returned to control concentrations in the presence of INS. However, serum GH levels were unchanged after INS therapy in the diabetic gilts. In conclusion, altered GH secretion in the diabetic gilt may, in part, be due to elevated CSF glucose concentrations, which may alter GH-releasing hormone and/or somatostatin secretion from the hypothalamus.
采用链脲佐菌素诱导5头8至12周龄的后备母猪患糖尿病。除实验期间外，后备母猪均用外源性胰岛素（INS）维持。4头同窝出生的后备母猪作为对照。9月龄时，所有后备母猪均进行卵巢切除，卵巢切除术后30天，进行实验1。插入颈静脉导管，每10分钟采集一次血样，共采集8小时。后备母猪11月龄时进行实验2。在无INS治疗（第一阶段）或有INS治疗（第二阶段）的情况下采集静脉血和脑脊液（CSF）样本。在实验1中，糖尿病后备母猪（465±17mg/100ml）的血浆葡萄糖浓度高于对照后备母猪（82mg±17mg/100ml）（P<0.05），而糖尿病后备母猪的血清INS较低（P<0.0001）（0.3±0.02对0.9±0.05ng/ml），糖尿病后备母猪和对照后备母猪的胰岛素样生长因子-I相似（分别为32±3对43±4ng/ml）。糖尿病后备母猪的平均血清GH浓度是对照后备母猪的2倍（P<0.02）（2.8±0.4ng/ml对1.2±0.2ng/ml）。糖尿病后备母猪的GH脉冲次数多于对照后备母猪（P<0.05）（分别为3.2±0.4对1.5±0.3/8小时）。此外，与对照后备母猪（3.3±0.6ng/ml）相比，糖尿病后备母猪的GH脉冲幅度明显升高（P<0.02）（5.8±0.4ng/ml）。糖尿病后备母猪的平均基础血清GH浓度高于对照后备母猪（P<0.07）（2.2±0.5ng/ml对1.0±0.1ng/ml）。在实验2中，糖尿病后备母猪和对照后备母猪在两个阶段的CSF中胰岛素样生长因子-I、INS、GH和蛋白质的浓度相似。第一阶段糖尿病后备母猪和对照后备母猪的血清GH水平相似，但第二阶段糖尿病后备母猪的血清GH水平高于对照后备母猪（P<0.05）。在有INS治疗（P<0.003）和无INS治疗（P<0.0002）的情况下，糖尿病后备母猪的CSF葡萄糖水平均高于对照后备母猪，而在无INS的情况下，糖尿病后备母猪的血浆葡萄糖高于对照后备母猪（P<0.003），但在有INS的情况下恢复到对照浓度。然而，糖尿病后备母猪接受INS治疗后血清GH水平未发生变化。总之，糖尿病后备母猪GH分泌的改变可能部分归因于CSF葡萄糖浓度升高，这可能会改变下丘脑促生长激素释放激素和/或生长抑素的分泌。
