マウス乳腺発育におけるProlactinおよびGrowth hormoneの重要性
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The effects of prolactin (PL) and/or growth hormone (GH) on mammary gland development in adrenalectomized-ovariectomized mice were investigated to examine how these mammotropins influence the gland in the apparent absence of steroid hormones.Animals used were C3H/He strain of female mice which had been bred in the authors' laboratory. They were divided into 5 groups consisted of 8 each at about 70 and 55 days of age in Experiments 1 and 2, respectively. In both experiments, group I was given no treatment and served as the intact control, and groups II-V consisted of adrenalectomized-ovariectomized animals. Group II was given no injection and served as the adrenalectomized-ovariec-tomized control. Groups III, IV and V received subcutaneous injections of 0.5 mg of PL (NIHP-B2), 1 mg of GH (NIH-GH-B12) and PL+GH twice daily, respectively. In Experiment 1, the injection was given for 7 days from the following morning of the operation of adrenalectomy and ovariectomy. In Experiment 2, it was given for 10 days beginning 7 days after the operation in order to examine the effects of these hormones on the once involuted mammary glands. All mice were killed on the morning following the last injections and the left third thoracic and the bilateral inguinal glands were used for the whole mount preparation and the determination of deoxyribonucleic acid (DNA) content, respectively. The mammary development in the whole mount preparation was graded from 1 to 4 in increments of 1 for either ductal branching or presence of end-buds.The increases in body weights were more marked in groups IV and V than in the other 3 groups, especially in Experiment 2 (Table 1).In Experiment 1, the intact control and all injected groups were significantly superior to group II in the ductal growth, except group IV which had a large variation (Figs. 1 and 2). No significant differences in the degree of the formation of end-buds were observed among groups, but group V appeared to be better than the other 4 groups in this measure. Mammary DNA content was significantly less in group II than in the other 4 groups (Fig. 3). DNA content in group V was higher than those in groups I and III.In Experiment 2, ductal developments in groups III, IV and V were more conspicuous than that in group II. Group V was significantly higher than groups I and II in the degree of end-bud formation (Figs. 4 and 5). The well developed end-buds and small alveoli were often observed in group III. The difference in mammary DNA content was not statistically significant among groups, but DNA contents of groups IV and V were comparable to that of group I (Fig. 6).In general, mammary gland was considerably involuted by removal of both adrenal glands and ovaries. PL, GH or PL+GH could prevent the gland from involution, and maintain the normal level. Furthermore, GH or PL+GH could restore the gland to the normal level even after the gland was once involuted almost completely. Prolactin was apparently effective on the formation of end-buds. The present results provide the definite evidence that PL and GH are the primary important mammotropins in mice.
- 社団法人 日本畜産学会の論文
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