Effect of growth hormone on mammary gland growth and lactation in mice with special reference of the relation with prolactin.

1. GH和乳腺生长1）GH和正常乳腺生长：每天两次向25 - 55日龄的C3 H/He处女小鼠注射5或50 ng SMS，导致与血浆GH水平降低相关的正常乳腺生长显著抑制。新生SHN雌性小鼠单次注射4 mg谷氨酸（MSG）也获得了类似的结果。同时，血浆催乳素（PRL）水平和发情周期的模式受任何处理的影响不大。血浆GH水平与正常乳腺生长呈显著的单相关，但在血浆PRL水平一定的情况下，二者之间不存在偏相关。2）GH与新生儿前期乳腺增生性肺泡结节（HAN）形成：新生儿单用MSG处理可抑制HAN的形成。GH与自发性乳腺肿瘤的发生：MSG降低血浆GH水平对自发性乳腺肿瘤的发生影响不大. GH与泌乳在C3 H/He小鼠中，每天两次注射50 ng SMS，血浆GH水平的慢性下降抑制了泌乳期第12天的正常乳腺生长，但SMS处理组和对照组之间的泌乳性能没有差异。它的作用常常被其它促乳激素PRL所掩盖。

1. GH and Mammary Gland Growth1) GH and normal mammary gland growth: Twice daily injections of 5 or 50 ng SMS to C3H/He virgin mice between 25 and 55 days of age resulted in a significant inhibition of normal mammary gland growth associated with the reduced plasma GH level. Similar results were also obtained by the neonatal single injection of 4 mg monosodium glutamate (MSG) to SHN female mice. Meanwhile, plasma prolactin (PRL) level and the pattern of estrous cycles were affected little by either treatment. There was the significant simple correlation between plasma GH level and normal mammary gland growth, but not the partial correlation when plasma PRL level was fixed.2) GH and preneolastic mammary hyperplastic alveolar nodule (HAN) formation: Single neonatal MSG treatment inhibited HAN formation. However, GH level had neither single nor partial correlation with HAN formation.3) GH and spontaneous mammary tumor development: Spontaneous mammary tumor development was affected little by reduced plasma GH level by MSG.2. GH and lactationIn C3H/He mice, chronic decline of plasma GH level by twice daily injections of 50 ng SMS suppressed normal mammary gland growth on day 12 of lactation, however, there was no difference in lactational performance between the SMS-treated and the control groups.All findings strongly suggest that while GH is an important hormone for normal mammary gland growth and lactation, its role is often masked by the other mammotropic hormones, PRL.