McArdle C A, Poch A, Käppler K
Institute for Hormone and Fertility Research, University of Hamburg, Germany.
Endocrinology. 1993 May;132(5):2065-72. doi: 10.1210/endo.132.5.7682940.
Atrial, brain-type, and C-type natriuretic peptides (ANP, BNP, and CNP) act via receptors with intrinsic guanylate cyclase activity. The A-type and B-type ANP receptors are selectively activated by ANP and CNP, respectively. The anterior pituitary is a site of ANP production and action, suggesting a local regulatory function, and this may also hold true for CNP which is found at its highest tissue concentrations in the anterior pituitary. Here we show that these peptides all cause dose-dependent increases in cGMP accumulation in alpha T3-1 cells (a gonadotrope-derived cell line), GH3 cells, and in primary cultures of rat pituitary cells. The response to CNP is particularly robust in alpha T3-1 cells (59 +/- 9-fold increase, EC50 14 +/- 3 nM), and the rank order of potency in alpha T3-1 cells and primary cultures (CNP >> ANP > BNP) is suggestive of action exerted via B-type receptors. Although CNP did not alter GnRH-stimulated LH release or [3H]inositol phosphate accumulation, GnRH reduced CNP-stimulated cGMP accumulation dose dependently (EC50 approximately 0.1 nM). This inhibition reflects the ability of GnRH to shift the CNP dose-response curve rightward (increasing the EC50 for CNP action approximately 10-fold both with and without 3-isobutyl-1-methylxanthine). The inhibitory effect was not blocked by omission of extracellular Ca++ nor mimicked by the Ca++ ionophore A23187 but was mimicked by a protein kinase C (PKC)-activating phorbol ester (which had a comparable effect to GnRH on the EC50 for CNP action). The data imply that CNP rather than (or in addition to) ANP may have a local regulatory function within the pituitary, that although its role is currently unknown it may involve functional interaction with GnRH in gonadotropes, and that the effect of GnRH on CNP action may be PKC-mediated. Moreover, we suggest that alpha T3-1 cells may be a useful model for investigation of the cross-talk between the B-type natriuretic peptide receptor-regulated signal transduction pathway and the Ca++/PKC pathway activated by ligand-stimulated hydrolysis of inositol phospholipids.
心房钠尿肽、脑型钠尿肽和C型钠尿肽（ANP、BNP和CNP）通过具有内在鸟苷酸环化酶活性的受体发挥作用。A型和B型ANP受体分别被ANP和CNP选择性激活。垂体前叶是ANP产生和作用的部位，提示其具有局部调节功能，对于在垂体前叶中组织浓度最高的CNP来说可能也是如此。在此我们表明，这些肽均能使αT3 - 1细胞（一种促性腺激素细胞系）、GH3细胞以及大鼠垂体细胞原代培养物中的cGMP积累呈剂量依赖性增加。αT3 - 1细胞对CNP的反应尤为强烈（增加59±9倍，EC50为14±3 nM），并且在αT3 - 1细胞和原代培养物中其效力顺序为（CNP >> ANP > BNP），这表明是通过B型受体发挥作用。尽管CNP不会改变GnRH刺激的LH释放或[3H]肌醇磷酸积累，但GnRH会剂量依赖性地降低CNP刺激的cGMP积累（EC50约为0.1 nM）。这种抑制反映了GnRH能够使CNP剂量反应曲线向右移动（无论有无3 - 异丁基 - 1 - 甲基黄嘌呤，CNP作用的EC50均增加约10倍）。这种抑制作用不会因省略细胞外Ca++而被阻断，也不会被Ca++离子载体A23187模拟，但会被蛋白激酶C（PKC）激活剂佛波酯模拟（其对CNP作用的EC50的影响与GnRH相当）。这些数据表明，CNP而非（或除了）ANP可能在垂体内具有局部调节功能，尽管其目前作用尚不清楚，但可能涉及与促性腺激素细胞中GnRH的功能相互作用，并且GnRH对CNP作用的影响可能是由PKC介导的。此外，我们认为αT3 - 1细胞可能是研究B型钠尿肽受体调节的信号转导途径与由配体刺激的肌醇磷脂水解激活的Ca++/PKC途径之间相互作用的有用模型。
