COUTINHO E M, CSAPO A
J Gen Physiol. 1959 Sep;43(1):13-27. doi: 10.1085/jgp.43.1.13.
If the excised, parturient rabbit uterus is repeatedly treated with a Krebs solution free from Ca, its tension in a tetanus drops gradually, and in 15 to 30 minutes becomes zero. We call such a uterus "Ca-deficient." The uterus in this condition has a high threshold, it is non-propagating, "inexcitable," fails to respond to oxytocics in a characteristic fashion, but retains maximum contractility. As Ca is gradually restored to the Krebs, these lost qualities return in a graded fashion and tension of the tetanized uterus becomes a log function of the [Ca]. If the [Ca] is kept low, i.e. 1/10 to 1/20 of the normal, tetanic tension is small but steady, and the preparation offers a full scale of tension increment for the measurement of oxytocic potency. Keeping the stimulus and the [Ca] constant, excitability (measured by tension increment) is a log function of the drug concentration. The recovery of excitability by restoring Ca to the Ca-deficient uterus is strongly temperature-dependent. The Ca-deficient uterus is a useful preparation for the study of the mechanism of regulation. When its excitability is partially recovered by Ca, the electrically stimulated uterus becomes an excellent tool for the quantitative measurement of oxytocic potency.
如果将切除的分娩兔子宫反复用不含钙的克氏溶液处理，其强直收缩时的张力会逐渐下降，在15至30分钟内变为零。我们称这样的子宫为“缺钙子宫”。处于这种状态的子宫阈值较高，不产生兴奋传播，“不兴奋”，对催产素无特征性反应，但保留最大收缩性。随着钙逐渐恢复到克氏溶液中，这些丧失的特性会以分级的方式恢复，强直收缩子宫的张力成为钙浓度的对数函数。如果将钙浓度保持在低水平，即正常水平的1/10至1/20，强直收缩张力虽小但稳定，并且该标本可为催产素效力的测量提供全面的张力增加范围。在刺激和钙浓度保持恒定的情况下，兴奋性（通过张力增加来衡量）是药物浓度的对数函数。通过向缺钙子宫中恢复钙来恢复兴奋性强烈依赖于温度。缺钙子宫是研究调节机制的有用标本。当通过钙使其兴奋性部分恢复时，电刺激的子宫成为定量测量催产素效力的极佳工具。
