Lee J T, Lebenthal E, Lee P C
Department of Pediatrics, Children's Hospital, State University of New York, Buffalo.
Pancreas. 1991 Jan;6(1):96-103. doi: 10.1097/00006676-199101000-00013.
The nuclear T3 receptors in rat pancreas exhibit a characteristic maturation pattern during development and are subjected to autologous regulation by thyroid hormones. To see if glucocorticoids also regulate T3 receptors in the pancreas, rats at various age groups were subjected to experimental conditions that altered their glucocorticoid status and the corresponding changes in nuclear T3 receptors, and exocrine enzymes in their pancreata were evaluated. Hydrocortisone administration to normal suckling and weaning rats did not change total T3 binding capacity or the dissociation constant as measured at 30 degrees C (Kd30). A significant increase in the degree of occupancy of the T3 receptor was found at 5-10 days after treatment with hydrocortisone (42.2 + 4.1% vs. 19.2 + 2.0%). T3 binding capacity and exocrine enzyme concentrations were significantly reduced in both adrenalectomized (Adx) pups and adults, indicating a continuous dependency on glucocorticoid from preweaning to adulthood. In adrenalectomized rat pups, either T4 or glucocorticoid replacement alone restored T3 binding capacity and exocrine enzyme concentrations. T4 and glucocorticoid were given together to Adx rats, the level of stimulation of both pancreatic T3 binding capacity and exocrine enzyme concentrations was found to be equal to the sum of the stimulation by each of these hormones when given alone. Furthermore, a good correlation was found between Bmax30 (Bmax measured at 30 degrees C, representing total sites) for T3 binding and exocrine enzyme activities in different groups following various experimental treatments. These findings provide further evidence that thyroxine can act directly on the rat pancreas presumably through the T3 receptor in regulating the postnatal development of the exocrine enzymes.
大鼠胰腺中的核甲状腺激素T3受体在发育过程中呈现出特征性的成熟模式，并受到甲状腺激素的自身调节。为了探究糖皮质激素是否也调节胰腺中的T3受体，对不同年龄组的大鼠进行实验处理，改变其糖皮质激素状态，评估胰腺中核T3受体的相应变化以及外分泌酶的情况。对正常哺乳和断奶大鼠给予氢化可的松，在30℃下测量时，总T3结合能力或解离常数没有变化（Kd30）。在用氢化可的松处理5 - 10天后，发现T3受体的占据程度显著增加（42.2 + 4.1%对19.2 + 2.0%）。肾上腺切除（Adx）的幼崽和成体中，T3结合能力和外分泌酶浓度均显著降低，表明从断奶前到成年期持续依赖糖皮质激素。在肾上腺切除的幼鼠中，单独给予T4或糖皮质激素替代均可恢复T3结合能力和外分泌酶浓度。将T4和糖皮质激素一起给予肾上腺切除的大鼠，发现胰腺T3结合能力和外分泌酶浓度的刺激水平等于单独给予每种激素时的刺激之和。此外，在各种实验处理后的不同组中，T3结合的Bmax30（在30℃下测量的Bmax，代表总位点）与外分泌酶活性之间发现了良好的相关性。这些发现进一步证明，甲状腺素可能通过T3受体直接作用于大鼠胰腺，调节外分泌酶的出生后发育。
