Robertson J A, Gallagher N D
Gastroenterology. 1979 Sep;77(3):511-7.
Experiments were designed to identify the factor in serum which has been shown to result in an increased number of intrinsic factor (IF) receptors in the small intestine of the mouse in late pregnancy. IF receptors for cobalamin (Cbl) were measured by determining the quantity of IF-57CoCbl bound in ileal homogenates. A Scatchard plot of the binding data confirmed that there was an increase in the number of IF receptors and revealed that there was a reduction in their affinity constant (K alpha). The K alpha for pregnant mice was 0.7 x 10(12) M-1 compared with 2.8 x 10(12) M-1 in nonpregnant mice. The number of receptors decreased between 2 and 4 hr after hysterectomy (Hx) in day 19 pregnant mice. Hourly injections of human placental lactogen (PL) maintained IF-Cbl binding at pregnant levels in the Hx mice. Growth hormone but not prolactin produced a similar response. The smallest quantity of PL which was effective was 1 microgram. Placental lactogen did not have an effect on IF-Cbl binding in nonpregnant female mice. Neither hypophysectomy nor ovariectomy affected IF-Cbl. It is proposed that placental lactogen is the serum factor which is responsible for the increased number of IF receptors in the pregnant mouse.
实验旨在确定血清中的一种因子，该因子已被证明会导致妊娠后期小鼠小肠中内因子（IF）受体数量增加。通过测定回肠匀浆中结合的IF-57CoCbl的量来测量钴胺素（Cbl）的IF受体。结合数据的Scatchard图证实IF受体数量增加，并显示其亲和常数（Kα）降低。妊娠小鼠的Kα为0.7×10¹² M⁻¹，而未妊娠小鼠为2.8×10¹² M⁻¹。在第19天妊娠小鼠子宫切除术后2至4小时内，受体数量减少。每小时注射人胎盘催乳素（PL）可使子宫切除术后小鼠的IF-Cbl结合维持在妊娠水平。生长激素而非催乳素产生类似反应。有效所需的最小PL量为1微克。胎盘催乳素对未妊娠雌性小鼠的IF-Cbl结合没有影响。垂体切除或卵巢切除均不影响IF-Cbl。有人提出胎盘催乳素是导致妊娠小鼠IF受体数量增加的血清因子。
