Jansson J O, Edén S, Isaksson O
Endocr Rev. 1985 Spring;6(2):128-50. doi: 10.1210/edrv-6-2-128.
The secretory pattern of GH in the mature rat is sexually differentiated. In male rats GH is secreted in pulses occurring at regular 3- to 4-h intervals. In females the pulses are lower and plasma GH levels between the pulses are higher than in males. The continuous presence of testosterone appears to be necessary to maintain low basal GH levels in adult male rats. Neonatal, but not prepubertal, gonadectomy decreases GH pulse height in adult male rats to female levels. Administration of testosterone neonatally to castrated animals returns GH pulse height to normal suggesting that neonatal testicular androgen secretion is one determinant for GH pulse height in adult male rats. Administration of testosterone neonatally or during adult life to neonatally ovariectomized rats also produces higher GH pulses. In contrast to testosterone, estrogens elevate basal plasma GH levels and suppress the GH pulses under some conditions. Estrogens may stimulate basal GH secretion by acting directly on the pituitary. The physiological significance of the secretory pattern of GH has been investigated in hypophysectomized rats by simulating different plasma patterns of GH. The results suggest that high, infrequent GH pulses with low plasma GH levels in between (i.e. a masculine plasma GH pattern) promotes growth more effectively than an intermediate, rather constant level of plasma GH (i.e. a feminine plasma GH pattern). Since male sex steroids masculinize the secretory pattern of GH and have only minor growth-promoting effects in hypophysectomized animals it appears that the growth promoting effect of androgens is indirect and is due to an altered secretory pattern of GH. Presumably, neonatal androgen secretion stimulates body growth during adult life by irreversibly masculinizing the secretory pattern of GH. In contrast, estrogens appear to influence body growth by mechanisms that are mainly independent of the secretory pattern of GH. Evidence is accumulating that the secretory pattern of GH in the rat also affects various sexually differentiated hepatic characteristics such as steroid metabolism and prolactin receptor concentration. Thus, a feminization of the liver develops after continuous, but not intermittent, administration of GH to hypophysectomized rats. GH secretion is predominantly regulated by two hypothalamic peptides; GRF, and the GH-release-inhibiting factor, somatostatin.(ABSTRACT TRUNCATED AT 400 WORDS)
成熟大鼠生长激素（GH）的分泌模式存在性别差异。在雄性大鼠中，GH以每隔3至4小时规律出现的脉冲形式分泌。在雌性大鼠中，脉冲幅度较低，脉冲间期的血浆GH水平高于雄性。成年雄性大鼠持续存在睾酮似乎是维持低基础GH水平所必需的。新生期而非青春期前进行性腺切除会使成年雄性大鼠的GH脉冲幅度降至雌性水平。给阉割动物新生期注射睾酮可使GH脉冲幅度恢复正常，这表明新生期睾丸雄激素分泌是成年雄性大鼠GH脉冲幅度的一个决定因素。给新生期卵巢切除的大鼠新生期或成年期注射睾酮也会产生更高的GH脉冲。与睾酮相反，雌激素在某些情况下会提高基础血浆GH水平并抑制GH脉冲。雌激素可能通过直接作用于垂体来刺激基础GH分泌。通过模拟不同的血浆GH模式，在垂体切除的大鼠中研究了GH分泌模式的生理意义。结果表明，高频率、低血浆GH水平的不频繁GH脉冲（即男性化的血浆GH模式）比中等、相对恒定的血浆GH水平（即女性化的血浆GH模式）更有效地促进生长。由于雄性类固醇使GH分泌模式男性化，而在垂体切除的动物中只有轻微的促生长作用，因此雄激素的促生长作用似乎是间接的，并且是由于GH分泌模式的改变。据推测，新生期雄激素分泌通过不可逆地使GH分泌模式男性化来刺激成年期的身体生长。相反，雌激素似乎通过主要独立于GH分泌模式的机制来影响身体生长。越来越多的证据表明，大鼠GH的分泌模式也会影响各种性别分化的肝脏特征，如类固醇代谢和催乳素受体浓度。因此，给垂体切除的大鼠持续但非间歇性地注射GH后，肝脏会出现女性化。GH分泌主要受两种下丘脑肽调节；生长激素释放因子（GRF）和生长激素释放抑制因子，即生长抑素。（摘要截断于400字）
