Phillip M, Palese T, Hernandez E R, Roberts C T, LeRoith D, Kowarski A A
Division of Pediatric Endocrinology, University of Maryland School of Medicine, Baltimore 21201.
Endocrinology. 1992 May;130(5):2865-70. doi: 10.1210/endo.130.5.1315260.
Circulating levels of insulin-like growth factor-I (IGF-I) increase during puberty, concurrent with an increase in the levels of GH and the gonadal steroids. The relationship between the changes observed in IGF-I and testosterone (T) levels are not understood. This study was designed to determine whether T has a direct effect on IGF-I serum levels, liver IGF-I gene expression, and epiphyseal growth plate IGF-I and IGF-I receptor gene expression. Hypophysectomized castrated rats were divided into four groups of six animals. The T group was treated with sc T for 5 days. The GH group was treated with a single dose of GH. The GH plus T group was treated with T for 5 days and with GH on the last day of treatment. The control group was injected for 5 days with vehicle alone. Serum IGF-I levels in the T group were not significantly different from those in the control group, and the levels in the GH plus T group were not significantly different from those in the GH group. There was an 11-fold increase in liver IGF-I mRNA abundance in the GH group compared to the control group (P less than 0.01). Liver IGF-I mRNA levels in the T group were not significantly different from those in the control group. When liver IGF-I mRNA levels in the GH plus T group were compared to those in the GH-treated group, no significant differences were found. In the epiphyseal growth plate region, there was a 12-fold increase in IGF-I mRNA levels in the GH group compared to those in the control group, but there was no statistical difference between the control and T groups. IGF-I mRNA levels in the GH plus T group were not significantly different from those in the GH-treated group. IGF-I receptor mRNA abundance was not significantly different in the T group compared to that in the control group. GH decreased IGF-I receptor mRNA by 2.3-fold, but T treatment before GH injection did not change this effect. We conclude that in castrated hypophysectomized rats, T does not stimulate IGF-I gene expression in the liver, nor does it increase IGF-I serum levels. T alone also does not have a stimulatory effect on IGF-I or IGF-I receptor gene expression in the epiphyseal growth plate region.(ABSTRACT TRUNCATED AT 400 WORDS)
青春期期间，胰岛素样生长因子-I（IGF-I）的循环水平会升高，同时生长激素（GH）和性腺类固醇水平也会增加。目前尚不清楚IGF-I和睾酮（T）水平变化之间的关系。本研究旨在确定T是否对IGF-I血清水平、肝脏IGF-I基因表达以及骨骺生长板IGF-I和IGF-I受体基因表达有直接影响。将垂体切除并阉割的大鼠分为四组，每组六只动物。T组皮下注射T 5天。GH组给予单剂量的GH。GH加T组注射T 5天，并在治疗的最后一天注射GH。对照组仅注射溶媒5天。T组的血清IGF-I水平与对照组无显著差异，GH加T组的水平与GH组无显著差异。与对照组相比，GH组肝脏IGF-I mRNA丰度增加了11倍（P小于0.01）。T组的肝脏IGF-I mRNA水平与对照组无显著差异。将GH加T组的肝脏IGF-I mRNA水平与GH治疗组相比，未发现显著差异。在骨骺生长板区域，与对照组相比，GH组的IGF-I mRNA水平增加了12倍，但对照组和T组之间无统计学差异。GH加T组的IGF-I mRNA水平与GH治疗组无显著差异。与对照组相比，T组的IGF-I受体mRNA丰度无显著差异。GH使IGF-I受体mRNA降低了2.3倍，但在注射GH前给予T治疗并未改变这种作用。我们得出结论，在垂体切除并阉割的大鼠中，T不会刺激肝脏中的IGF-I基因表达，也不会增加IGF-I血清水平。单独使用T对骨骺生长板区域的IGF-I或IGF-I受体基因表达也没有刺激作用。（摘要截断于400字）
