Wright M L, Cykowski L J, Lundrigan L, Hemond K L, Kochan D M, Faszewski E E, Anuszewski C M
Biology Department, College of Our Lady of the Elms, Chicopee, Massachusetts 01013.
J Exp Zool. 1994 Oct 1;270(2):175-88. doi: 10.1002/jez.1402700207.
The effect of prolactin, growth hormone, and various adrenal corticoids on hindlimb growth, development, and differentiation was studied in Rana pipiens larvae. Experiments were performed at different stages of spontaneous development and during metamorphosis induced in premetamorphic tadpoles by various concentrations of exogenous T4. Prolactin at 10 micrograms/day inhibited the limb at spontaneous premetamorphosis, had no effect at prometamorphosis or when administered with 3.8 nM T4, and synergized with T4 at 63 nM T4 and above. Growth hormone (10 or 20 micrograms/day) promoted limb growth and development during premetamorphosis but had no effect on spontaneous or induced metamorphosis thereafter, nor did it stimulate limb epidermal differentiation. The adrenal corticoids inhibited limb growth and epidermal cell proliferation during pre- and prometamorphosis but had no effect on limb morphogenesis or differentiation. The depressive effect of corticoids during spontaneous metamorphosis is at least partly through thyroid inhibition since hydrocortisone significantly reduced follicle cell height, lumen diameter, and cell proliferation in the thyroid. During induced metamorphosis, steroids (0.29 microM), especially corticosterone and aldosterone, antagonized the effect of 0.38 to 1.2 nM T4 on the limb. All steroids except deoxycorticosterone synergized with 3.8 nM T4, and at 31 nM T4, approximating the climax level with permeability factors taken into account, all corticoids synergized with T4 to promote limb growth and development. Aldosterone antagonized T4 at a higher T4 level than the other corticoids. The effect of all steroids except corticosterone was also corticoid dose-dependent. The results show the importance of the T4 concentrations in interactions of T4 with other hormones and suggest a scheme for hormonal control of limb growth and morphogenesis during metamorphosis. During premetamorphosis growth hormone synergizes with low endogenous T4 to promote initial limb growth and development while prolactin opposes this action. During prometamorphosis, as growth hormone and prolactin become ineffective corticosteroids begin to synergize with the rising level of endogenous T4. At climax, prolactin also augments the action of T4 to bring about rapid hindlimb growth.
研究了催乳素、生长激素和各种肾上腺皮质激素对豹蛙幼体后肢生长、发育和分化的影响。实验在自发发育的不同阶段以及由不同浓度外源性甲状腺素（T4）诱导前变态期蝌蚪变态的过程中进行。每天10微克的催乳素在自发前变态期抑制肢体生长，在前变态期或与3.8纳摩尔T4一起给药时无作用，而在63纳摩尔及以上的T4浓度时与T4协同作用。生长激素（每天10或20微克）在前变态期促进肢体生长和发育，但此后对自发或诱导的变态无作用，也不刺激肢体表皮分化。肾上腺皮质激素在前变态期和前变态期抑制肢体生长和表皮细胞增殖，但对肢体形态发生或分化无作用。皮质激素在自发变态期间的抑制作用至少部分是通过抑制甲状腺实现的，因为氢化可的松显著降低了甲状腺中滤泡细胞高度、管腔直径和细胞增殖。在诱导变态期间，类固醇（0.29微摩尔），尤其是皮质酮和醛固酮，拮抗0.38至1.2纳摩尔T4对肢体的作用。除脱氧皮质酮外的所有类固醇都与3.8纳摩尔T4协同作用，在31纳摩尔T4时，考虑到通透性因子接近高潮水平，所有皮质激素都与T4协同作用以促进肢体生长和发育。醛固酮在比其他皮质激素更高的T4水平时拮抗T4。除皮质酮外的所有类固醇的作用也呈皮质激素剂量依赖性。结果表明T4浓度在T4与其他激素相互作用中的重要性，并提出了变态期间肢体生长和形态发生的激素控制方案。在前变态期，生长激素与低水平的内源性T4协同作用以促进肢体的初始生长和发育，而催乳素则对抗这种作用。在前变态期，随着生长激素和催乳素变得无效，皮质类固醇开始与内源性T4水平的升高协同作用。在高潮期，催乳素也增强T4的作用以实现后肢的快速生长。
